> I know from the documentation that the FOR implicitly opens a cursor, > but I'm wondering if there would be any performance advantages to > explicitly declaring a cursor and moving through it with FETCH commands? As of PostgreSQL 7.1.x, cursors may only be defined as READ ONLY, and the FOR clause is therefore superfluous. Example 7-42. 40.7.1. Hopefully the … The only rationale for using a cursor FOR loop for a single-row query is that you don’t have to write as much code, and that is both dubious and a lame excuse. For prior versions, you need to create a function and select it. If you're looking for the PostgreSQL equivalent of, for example, iterating through a result with a cursor on SQL Server, that's what it is. This is a guide to PostgreSQL For Loop. A special flag "auto-held" marks > such cursors, so we know to clean them up on exceptions. 41.7.1. Cursors VS Loops ” Add yours. However, when you use the reverse option, the for loop subtracts the step from loop_counter. Recommended Articles. Declaring Cursor Variables. Might as well stick with the simpler notation. ; Second, the from and to are expressions that specify the lower and upper bound of the range. By default, the for loop adds the step to the loop_counter after each iteration. Example. All access to cursors in PL/pgSQL goes through cursor variables, which are always of the special data type refcursor.One way to create a cursor variable is just to declare it as a variable of type refcursor.Another way is to use the cursor declaration syntax, which in general is: Doesn’t this look silly: 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.. You can think of a cursor as a name for a result set. The record variable is local to the cursor FOR LOOP statement. 1) record. All access to cursors in PL/pgSQL goes through cursor variables, which are always of the special data type refcursor.One way to create a cursor variable is just to declare it as a variable of type refcursor.Another way is to use the cursor declaration syntax, which in general is: Declaring Cursor Variables. Monkeygrind says: Nov 18, 2017 at 5:15 pm. Wow, thanks for doing all this work to get data. > As alluded to in earlier threads, this is done by converting such > cursors to holdable automatically. With PostgreSQL from 9.0, you can simply drop into executing plpgsql using a "DO" block. PostgreSQL cursor example. Besides this, even the result set retrieved from a particular query can be iterated using for loop in PostgreSQL. The for loop can be used effectively and conveniently as per our necessity to loop around or execute certain statements repetitively. It means that you can only reference it inside the loop, not outside. AFAICS it'd be exactly the same. Declaring a cursor A cursor FOR loop is designed to fetch all (multiple) rows from a cursor. On Tue, 20 Feb 2018 09:11:50 -0500 Peter Eisentraut <[hidden email]> wrote: > Here is a patch that allows COMMIT inside cursor loops in PL/pgSQL. GitHub Gist: instantly share code, notes, and snippets. I remember being advised against cursors once SQL 6.5 came out and finally got rid of them once we had table variables. The record is the name of the index that the cursor FOR LOOP statement declares implicitly as a %ROWTYPE record variable of the type of the cursor.. Direct cursor support is new in PL/pgSQL version 7.2. In this syntax: First, the for loop creates an integer variable loop_counter which is accessible inside the loop only. After the cursor FOR LOOP statement execution ends, the record variable becomes undefined. Example 7-42 begins a transaction block with the BEGIN keyword, and opens a cursor named all_books with SELECT * FROM books as its executed SQL statement. 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