Postgresql cursor example In PostgreSQL, a cursor is a database object that allows you to traverse the result set of a query one row at a time. Cursors generated from the same connection Similar to Oracle PL/SQL cursors, PostgreSQL has PL/pgSQL cursors that enable you to iterate business logic on rows read from the database. Specifies how the driver transforms JDBC escape call syntax into underlying SQL, for invoking procedures or functions. By using PostgreSQL cursor syntax, developers can This example shows how to call the PostgreSQL® built-in function, upper, which simply converts the supplied string argument to uppercase. You need to pass values to it. Since you cannot loop in SQL, you'll have to use PL/pgSQL, for example with a DO statement. IF EXISTS(SELECT 1 FROM sys. Cursors and transactions serve as the basic building blocks for creating database applications. Cursor self is like pointer without any value. if NEW. On the Let us take a look at an example now: If the query is executed as cursor you will notice that PostgreSQL goes for an index scan to speed up the creation of the first 10% of the data. To work with cursors the caller have to start a transaction. Examples of DECLARE a cursor. The query must be a SELECT, or something else that returns rows (such as EXPLAIN). There a number of restrictions which will make the driver silently fall back to fetching the whole ResultSet at once. But if you really want a CURSOR then you have to FETCH rows from it and return the results. The connection class is what creates cursors. Example 1 Important Note: The cursor remains open until the end of transaction, and since PostgreSQL works in auto-commit mode by default, the cursor is closed immediately after the procedure call, so it is not available to the caller. Postgresql: how to get names of cursors returned by function? 0. JPA 2. execute("fetch forward 100 from foo") You cannot use a cursor name like a table. As an example, if a query returns a value of one from an integer column, you would get a string of 1 with a default cursor, whereas with a binary cursor you would get a 4-byte field containing the internal representation of WHERE CURRENT OF statements are visible in that same cursor. Table of Contents. Do not forget to RETURN vref_cursor. This is a simple example to print some data only. Let's consider an example that fetches the first four rows stored in the result set, pointed to by the order_cur cursor. player_id, registration. What you've written looks suspiciously like a SQL Server cursor loop construct, and you don't need to do that. If the memory consumed by 2000 rows is light, increase that number. Remember that you are answering the question for readers in the future, and those people might not know the reasons for your code suggestion. In a database, cursors are the canonical way of iterating through result sets. PostgreSQL treats these statements like all other data changing statements The cursor is a client-side cursor for PostgreSQL. id) related_stuff_entries, array (SELECT As an example, if a query returns a value of one from an integer column, you would get a string of 1 with a default cursor whereas with a binary cursor you would get a 4-byte field containing the internal representation of the value (in big-endian byte order). For simple queries PostgreSQL will allow backwards fetch from cursors not declared with SCROLL, but this behavior is best not relied on. This guide will cursor must be the name of a refcursor variable that references an open cursor portal. In general, that looks like this:. Explicit (unbound) cursor. demo. If you had selected e. Npgsql 2. Prior to PostgreSQL 16, bound cursor variables were initialized to contain their own names, rather than being left as null, so that the underlying portal name would be the same as the cursor As an example, if a query returns a value of one from an integer column, you would get a string of 1 with a default cursor, whereas with a binary cursor you would get a 4-byte field containing the internal representation of the value (in In PostgreSQL, cursors are insensitive by default, and can be made sensitive by specifying FOR UPDATE. Cursor declarations in PL/pgSQL support SCROLL, but not WITH HOLD, for the historical reason that PostgreSQL functions always run inside a single transaction. In Python, you can use the psycopg2 adapter for PostgreSQL to create cursors. Something along the lines: SELECT id, title, array (SELECT (rs. sql. After that, check if there is more row left to fetch. CallableStatement, use the connection parameter escapeSyntaxCallMode with the values call or callIfNoReturn and specify no return parameter. So I want to loop those records and parse that json using query something like . col2, rs. An example: OPEN curs1 FOR SELECT * FROM foo WHERE key = mykey; 41. hibernate. MyCalendarDto' to 'org. BEGIN IF EXISTS(SELECT * FROM accounts a WHERE a. CREATE TYPE soh AS (ID integer, I had a task similar to this one. springframework. I have three tables product master sales data table I've written a function in postgresql for updating a table using two cursors, the code executes fine without errors but doesn't do anything. In PostgreSQL, triggers can only call procedures and the procedures must be largely self-contained. getArray(), but you lose the meta information about column names in the anonymous records. The holy grail of PostgreSQL cursor record count methods we've all been waiting for. As you have obfuscated the names of As an example, if a query returns a value of one from an integer column, you would get a string of 1 with a default cursor, whereas with a binary cursor you would get a 4-byte field containing the internal representation of WHERE CURRENT OF statements are visible in that same cursor. Another option is to return an array of (anonymous) records. If you don't want to assign the name, simply cast the function result to text, that will give you the cursor name. Implicit cursor Example: Write a stored procedure to select the customers renting from store_id =2. 0. Cursors in Python using the PostgreSQL psycopg2 adapter. However About cursor_tuple_fraction. How to use a Function Parameter in a Cursor that's incorporated with Dynamic SQL in Postgres Functions? 0. So you need to access the column inside the record to Created this Postgres Function which is working fine, but the actual requirement is to pass the input parameter in the function to the Cursor which uses the dynamic SQL as follows, The below is the Preamble. A Cursor’s execute method saves the query result This below code is a cursor in PostgreSQL 9. This example uses a cursor FOR loop: @Matthias, you are right! I did your suggestion and all works fine! tks a lot! Only one observation: the tutorial that you suggest me has a example with: open cur_films(p_year);. Using the methods of it you can execute SQL statements, fetch data from the result sets, call procedures. Declare a cursor in PL/pgSQL to be used with any query. Hot Network Questions Why would rebel factions capturing Aleppo make it safer to return to? org. If there is a row with that name, the cursor is open. As a direction is not specified, FORWARD is postgresql cursor "fetch into" loop doesn't return any data. Here are two different examples to declare this type of cursor. CALL GET_MTG(O_MTG_CURSOR,O_SQLCODE,O_SQLMSG ); Is there any way to pass the cursor as a parameter and have it return the results from the called stored procedure? 38. Cursors can be useful when you deal with large result sets or when you need to process rows sequentially. PL/SQL cursor example. Example The cursor returns a record, not a scalar value, so "tablename" is not a string variable. Declare curs3 CURSOR (key integer) FOR SELECT * FROM tenk1 WHERE unique1 = key; But when I input For this example, we’ll use a compound cursor based on both the created_at timestamp and the id of the last product fetched. Hence, you cannot use the special syntax WHERE CURRENT OFcursor. It is important that you assign the name before you open the cursor. You can think of a cursor The following diagram illustrates how to use a cursor in PostgreSQL: First, declare a cursor. Hot Network Questions Name that logic gate! CREATE OR REPLACE FUNCTION curson_func ( start_date timestamp, end_date timestamp) RETURNS SETOF integer AS $$ DECLARE level_cursor CURSOR FOR SELECT login_event. . Return results from cursor as table. 3 ERROR cursor does not exist after first loop in PL/pgSQL. Create trigger – Show you how to create your first trigger in PostgreSQL. Other products may work As the documentation describes here, I need to declare a cursor that accepts arguments at OPEN time. When CURSOR is declared with a select statement, DB will execute the select statement and then have the result stored in DB memory. Additionally to cur. Why isn't fetch showing data from refcursor in Postgres? 1. prepareCall ("{? = call upper( ? One notable limitation of the current support for a ResultSet created from a refcursor is that even though it is a cursor backed ResultSet, all data will be retrieved and I'm rookie to plpgsql, I've created a stored procedure to get the table data into refcursor and I'm trying to call the procedure from plpgsql and c# to check if the procedure/c# code is working fin As an example, if a query returns a value of one from an integer column, you would get a string of 1 with a default cursor, whereas with a binary cursor you would get a 4-byte field containing the internal representation of the value In PostgreSQL, cursors are insensitive by default, and can be made sensitive by specifying FOR UPDATE. my cursor has a select from multiple table and i don't know how to get the rowtype. How to get output to show PL/SQL cursor. statements are one or more SPL statements. Cursor in PostgreSQL: The cursor efficiently manages memory and enhances application performance while processing rows one at a time. LinkedCaseInsensitiveMap' Need to be mentioned that I'm obligated to use this exactly function and can't change it. id = NEW. As we already mentioned, this type of cursor pre-fetches all available rows for a SQL query. How to pass a table name for a cursor as function parameter? 0. How to use a Function Parameter in a Cursor that's incorporated with Dynamic SQL in Postgres Functions? 1. The concatenation turns the record into a string that looks like this (sql_features). DECLARE c1 refcursor; The variable c1 is unbound Inconvertible types; cannot cast 'com. We will use By default the data read by the cursor is "insensitive" (a snapshot from when the cursor was first created), but I would like the latest data for each row with FETCH in case there has been a subsequent update. In your case, that could look like this: You don't need a CURSOR at all to do this, you don't even need a function. Lock row in function Example 5. Here’s a basic example of cursor-based pagination using the id as the cursor: SELECT * FROM posts WHERE id >= :cursor LIMIT 10; Replace : you’re now equipped to implement efficient cursor-based pagination in your PostgreSQL databases, improving both application performance and user satisfaction. I went through the table, took the value from the cursor and wrote to another table with generate new ID. Step-by-Step Implementation of Cursor-Based Pagination 1. spring-data-jpa 1. 3 Function with cursor in postgreSQL. 0; this is mentioned in our migration nodes for 3. You first have to FETCH a result row into a record variable, then you can use that. HibernateException: PostgreSQL supports only one REF_CURSOR parameter, but multiple were registered There is only a single ref cursor declared! In fact, if I just register the single REF_CURSOR parameter and hardcode in a value for my Postgresql function for the WHERE date_ = date, this call works just fine. Using PL/SQL Cursor Variable with REF CURSOR to Fetch Data Dynamically. A cursor is an instance of Submittable and should be passed directly to the client. After evaluating each row, I insert the result to a table (EventLog_Main). id) THEN RAISE NOTICE ''Id is used''; -- better RAISE EXCEPTION END IF; RETURN NEW; END; second nonsense Introduction to cursors in PostgreSQL. In database management, cursors are essential for navigating through rows returned by a query while having the ability to process each row individually. We will also see the dangers involved and how to properly use WITH HOLD cursors in a PL/pgSQL procedure. id = xyx then Why you don't do. For prior versions, you need to create a function and select it. method, but this will get slower and slower, depending on the amount of data. g. Example Programs # These examples and others can be found in the directory src/test/examples in the source code distribution. 7. cursor is the name of a previously declared cursor. There are two types of cursor : 1. This is the table: While this code snippet may be the solution, including an explanation really helps to improve the quality of your post. There must be at least one statement. The cursor variable is opened and given the specified query to execute. Let’s If you want to avoid locking rows for a long time, you could also define a cursor WITH HOLD, for example using the DECLARE SQL statement. This feature was dropped from Npgsql 3. Procedures, introduced in PostgreSQL v11, support transaction commands like COMMIT and Answer for 1. So I write: cur = con. Cursors provide a way to fetch a small number of rows at a time, which can be useful for processing large result sets without consuming excessive memory. You can create Cursor object using the cursor() method of the Connection object/class. Drop trigger– Describe steps for using the DROP TRIGGER statement to delete a trigger from Now , I can use the following SQL commands to call this function and manipulate the returned cursor ,but the cursor name is automatically generated by the PostgreSQL BEGIN; SELECT function_1(); --It will output the generated cursor name , for example , "<unnamed portal 11>" ; FETCH 4 from "<unnamed portal 11>"; COMMIT; I need help with my "postgresql nested cursors" code. Cursors are typically used within applications that maintain a persistent connection to the PostgreSQL backend. If the entire resultset is fetched, PostgreSQL will go for a sequential scan and sort the data because the index scan is considered to be too expensive: Notes. Examples: FETCH curs1 INTO rowvar; FETCH curs2 INTO foo, bar, baz; FETCH LAST PL/pgSQL supports the use of cursors to retrieve and manipulate result sets from SQL queries in PostgreSQL database. How to use FETCH depends on the environment I have got a cursor, it is pointing to a SELECT, but this select is generated dynamically. My query looks something similar to: DECLARE cur CURSOR (argName character varying) FOR SELECT * Important Note: The cursor remains open until the end of transaction, and since PostgreSQL works in auto-commit mode by default, the cursor is closed immediately after the procedure call, so it is not available to the caller. I use PostgreSql 13. util. Cursors are useful when query results into a large number of record sets or Summary: in this tutorial, you will learn about the PL/pgSQL Cursors and how to use them to process a result set, row by row. You have to returns the results as a SETOF sometype because you can not combine a CURSOR with RETURNS TABLE. My plan is to get rows of data from a table (Admissions) using the "outer cursor" and evaluating each row using criteria from another table (EventLog_Staging). Update the score from the Geeks table using FOR UPDATE. For example lets say you are updating 10 million rows and an exception is thrown at the 6th million record the the update will fail and then it will rollback all of the rows that were updated prior to the failure. x had a feature whereby it automatically "dereferenced" cursors returned from functions. 0 nested cursor loop in postgresql. this attribute returns INVALID_CURSOR. execute('DELETE FROM [my_table_name] RETURNING [column_name, let's say id]') In SQL Server I used following SQL to find an open cursor and closing it in a 'catch' block. The problem is, I am passing the value of a column from the returned record To name the cursor, simply assign a string to the refcursor variable:. From the documentation of PostgreSQL I found that I can use . 1 StoredProcedureQuery with PostgreSQL and REF_CURSORs. query method. OPEN FOR query OPEN unbound_cursor [[NO ] SCROLL ] FOR query;. registration LEFT JOIN "fish-tsg". 22. The query With c9, should PostgreSQL use the value of p_plan_version_id as it is in the DECLARE section, or as it is when you OPEN c9?To resolve this ambiguity, you need to pass both parameters when you open the cursor: DECLARE c9 CURSOR (p_product_code varchar, p_pvi numeric) FOR SELECT product_code, terminal_code, quantity FROM product_stock constructor new Cursor(text: String, values: Any[][, config: CursorQueryConfig]) Instantiates a new Cursor. Example: OPEN c FOR SELECT id FROM a WHERE ok; LOOP UPDATE b SET a_ok = TRUE WHERE a_id = c. cursor(name='cursor_x') query = "select * from t" cursor. I use the system column ctid instead to determine the row without knowing the name Your example has no sense (you can't compare scalar value with cursor). Binary cursors should be used carefully. 0, you can simply drop into executing plpgsql using a "DO" block. However Let's understand both methods with the help of examples. When the CURSOR is closed, record is an identifier assigned to an implicitly declared record with definition cursor%ROWTYPE. A PL/pgSQL cursor allows you to encapsulate a query and process With PostgreSQL from 9. PostgreSQL doesn't have any problems with cursors, use them when you handle large amounts of data. 1. The implicit cursor type is created automatically by a database when a user uses the FOR clause in a SELECT statement. Function with cursor in postgreSQL. 0, and the discussion is in this issue. Other products may work differently. As the documentation says:. The PostgreSQL® JDBC driver implements native support for the Java 8 Date and Time API(JSR-310) using JDBC 4. Load 7 more related questions Show fewer related questions Sorted by: Reset to default Know someone who can answer? Share a link to this question via email, Twitter, or The cursor class Enables Python scripts to use a database session to run PostgreSQL commands. A cursor is very important in PostgreSQL, using a Cursors in PostgreSQL, it is possible to encapsulate the query instead of executing a whole query at once; after encapsulating query, it is possible to read a few rows from the result set, the main purpose of doing this is to avoid memory consumption of database server if the NOTE: The following examples do not reset the cursor position back to 0 as with the original example, Using MOVE instead of FETCH. Since the cursor is simply returned and isn't dereferenced, Npgsql returns the cursor name itself (unnamed portal 1); you can now fetch The SCROLL and NO SCROLL options have the same meanings as for a bound cursor. c_Data CURSOR FOR select dst_description , cnt_number , prd_name , grt_code , res_currency , res_date , prm_installmentdate from tbl_xxx, tbl_yyy, tbl_aaa where cnt_id = res_xxx and PostgreSQL Cursor Insert Example In PostgreSQL, cursors are used to retrieve and manipulate rows from a query result. Table 5. Cursors avoid the need to read the complete result set at once, which reduces the memory consumption. Why is it that adding parameters to the Dynamically generated CURSOR in Postgresql. Cursors are not visible inside the command. model. country_id FROM "fish-tsg". example. execute("declare foo cursor for select * from generate_series(1,1000000)") cur. EXECUTE is not a "clause", but a PL/pgSQL command to execute SQL strings. Cursors are particularly useful when you need to work with large result sets or when you want to In PostgreSQL, cursor is a database object that allows you to traverse the result set of a query one row at a time. 1. Here is a self-contained example: I want to know how CURSOR and FETCH work internally in PostgreSQL. Fetching rows from a cursor PostgreSQL. Locking row that is being currently inserted to avoid race conditions when reading same. 6. It looks to me from your example like you are trying to do things the Oracle way. Next Article: 3 Ways to See the Structure of a A cursor in PostgreSQL is a read-only pointer to a fully executed SELECT statement's result set. id; END LOOP; There are two types of cursors in Postgres: the implicit and the explicit/declare cursor types. Modify the function to take a refcursor as argument and instead execute the MOVE cursor statement directly which then makes 32. 2. CallableStatement upperFunc = conn. Example 32. Postgres cursor. 0. Postgres , handling multiple cursors for one query results. Working example: CREATE FUNCTION my_func(arg1 text, arg2 text, vref_cursor refcursor) RETURNS refcursor AS $$ BEGIN OPEN vref_cursor FOR SELECT generate_series(1,3); RETURN vref_cursor; END; $$ LANGUAGE plpgsql; BEGIN; SELECT Examples (these use the cursor declaration examples above): OPEN curs2; OPEN curs3(42); OPEN curs3(key := 42); Because variable substitution is done on a bound cursor's query, there are really two ways to pass values into the cursor: either with an explicit argument to OPEN, or implicitly by referencing a PL/pgSQL variable in the query. For example, if your result count is three million, an itersize value of 2000 (the default value) will result in 1500 network calls. The SQL i want to know if it is possible to get "Rowtype" for a cursor in postgresql (pl/pgsql). At the first, I assumed that . When a query is ready to be run, PostgreSQL I would like to use cursor in a function with the table name as a function variable, a simple example would be a select query through cursor. Here is my code: CREATE TABLE q_39442172 ( id character varying, event_id character varying, createdat character varying ); in GET_MTG(O_MTG_CURSOR ,O_SQLCODE,O_SQLMSG ); When I try to call the same stored procedure in postgres, the cursor is null. In essence you are going to have to refactor your code a bit. the schemaname with the tablename, the text representation of the record would have been (public,sql_features). dm_exec_cursors(@@SPID) WHERE [name] = 'Crsr_IDs' AND IS_OPEN = 1) BEGIN For example: do $$ declare Crsr_IDs refcursor = 'Crsr_IDs'; begin begin close Crsr_IDs; exception when invalid_cursor_name or That is simple. itemid = item. Then, fetch rows from the result set into a target. I have done an example working and another example NOT working. If There are several ways: Use an explicit cursor in PL/pgSQL and loop through it and process each result row. I also do not see any uses of cursors anywhere in your code so the question may be misleading. PostgreSQL treats these statements like all other data changing statements The Cursor class of the psycopg library provide methods to execute the PostgreSQL commands in the database using python code. execute(query) for row in cursor: print row To use a returning cursor function execute it as usual: OPEN cursor_name; Code language: PostgreSQL SQL dialect and PL/pgSQL (pgsql) In this syntax, the cursor_name is the name of the cursor declared in the declaration section. When you open a cursor, Oracle parses the query, binds variables, and executes the associated SQL statement. SQL Server has/had problems with cursors, MySQL can't handle cursors outside stored functions, that might be the reason some dba's don't like cursors. You have to assign a name to the cursor variable, then you can search for that cursor in pg_cursors. Next, open the cursor. 11. The solution to that is to use FOR UPDATE in the cursor query to make it "sensitive," but that is not allowed together with WITH HOLD. escapeSyntaxCallMode = String. Cursor in select statement in plain PostgreSQL. DECLARE ref refcursor := ''willi''; Then the portal will have that name. cursor = conn. Your second cursor declaration won't work as a static cursor declaration, because the value fetched from the first cursor changes. If you're looking for This article provides a comprehensive guide to cursors in PostgreSQL, covering the different types of cursors available, the operations that can be performed, and best practices for optimizing performance - read on! Processing a result set using a cursor is similar to processing a result set using a FOR loop, but cursors offer a few distinct advantages that you'll see in a moment. cursor() cur. WITH HOLD cursors in PL/pgSQL procedures. col3) FROM related_stuff RS WHERE rs. Query Execution in Postgresql. A cursor can be created by calling the connection object’s cursor() method. That can be retrieved using ResultSet. Supported Java 8 Date and It is easier to let psycopg2 do the server side cursor creation work just by naming it:. Use IN parameter to pass a cursor name. In PostgreSQL you can use the non-standard statement DECLARE to explicitly create a cursor, but usually you use client API functions or PL/pgSQL FOR loops that After some experimenting it seems like PostgreSQL behaves like this: Fetching many rows with SELECT * FROM large will not create a temporary file on the server side, the data are streamed as they are scanned. Prior to PostgreSQL 16, bound cursor variables were initialized to contain their own names, rather than being left as null, so that the underlying portal name would be the same as the cursor Examples (these use the cursor declaration examples above): OPEN curs2; OPEN curs3(42); OPEN curs3(key := 42); Because variable substitution is done on a bound cursor's query, there are really two ways to pass values into the cursor: either with an explicit argument to OPEN, or implicitly by referencing a PL/pgSQL variable in the query. cursor() method: They are permanently connected to the connection, and all instructions are run in the context of the database session covered by the connection. The PL/SQL block should open a cursor for a dynamic query that selects all columns You rarely need to explicitly use cursors in postgresql or pl/pgsql. I want to fetch my records by joining more than one table and i am getting JSON data from that join. When I can open a cursor without name the parameters and when I can't? – There are scenarios where a cursor is needed. Let's create a PL/SQL block that utilizes a cursor variable with REF CURSOR to dynamically fetch and display data from the "employees" table. If you create a server side cursor with a function that returns refcursor and fetch rows from the cursor, all returned rows are collected on the server first. When FETCH is called on the CURSOR, DB will just read the result moving on the CURSOR. However To call procedures using a java. I want to assign the statement after the declarement. If the cursor is declared with NO SCROLL, no I've written a function in postgresql for updating a table using two cursors, the code executes fine without errors but doesn't do anything. Also, you can only FETCH a single row at a time from a PL/pgSQL cursor. generate_id() - for generate new unique id; table_source - table where we take the vale; table_target - table where we write down; And then we create function with cursor and save what we need: As an example, if a query returns a value of one from an integer column, you would get a string of 1 with a default cursor, whereas with a binary cursor you would get a 4-byte field containing the internal representation of the value In PostgreSQL, cursors are insensitive by default, and can be made sensitive by specifying FOR UPDATE. The cursor cannot be open already, and it must have been declared as an unbound cursor (that is, as a simple refcursor variable). 1, “Processing a Simple Query in JDBC Cursor based ResultSets cannot be used in all situations. Basic PostgreSQL Triggers. Also, you can use "PERFORM" instead of "EXECUTE" to run a query and discard the results: this will avoid re-parsing the query each time (although it can't avoid dblink parsing the query each PostgreSQL allows you to delete rows and return values of columns of the deleted rows using this syntax: DELETE FROM [table_name] RETURNING [column_names] I would like to use this syntax in Python with using psycopg2 library. PostgreSQL is different. Creating a Cursor A cursor is created using the DECLARE. The cursor should be declared with the SCROLL option if one intends to use any variants of FETCH other than FETCH NEXT or FETCH FORWARD with a positive count. This article describes how cursors and transactions interact and how WITH HOLD can work around their limitations. login_event USING (player_id) WHERE ts >= start_date AND ts <= end_date ; Examples (these use the cursor declaration examples above): OPEN curs2; OPEN curs3(42); OPEN curs3(key := 42); Because variable substitution is done on a bound cursor's query, there are really two ways to pass values into the cursor: either with an explicit argument to OPEN, or implicitly by referencing a PL/pgSQL variable in the query. Solution: CREATE OR REPLACE PROCEDURE customer_rental_information(store_num The SCROLL and NO SCROLL options have the same meanings as for a bound cursor. They can encapsulate the query and read the query results a few rows at a time. Return multiple resultset from a function in Dynamically generated CURSOR in Postgresql. Introduction to PostgreSQL trigger – Give you a brief overview of PostgreSQL triggers, why you should use triggers, and when to use them. Such cursors can be used across transaction boundaries, Cursor based records in PostgreSQL. Examples of PL/SQL Updatable Cursors Example 1: Updating Rows in a Table Using FOR UPDATE. libpq Section 1. fetchmany(n) you can use PostgreSQL cursors: cur. OFFSET . col1, rs. 16 I am new to postgresql, and get a problem about nested loop. In PostgreSQL, cursor is a database object that allows you to traverse the result set of a query one row at a time. . vcm azuu utlc suop kigemi scffjz uiirva kcn hmma lycgtvd