Cursors VS Loops ” Add yours. Monkeygrind says: Nov 18, 2017 at 5:15 pm. Wow, thanks for doing all this work to get data. A cursor FOR loop is designed to fetch all (multiple) rows from a cursor. However, when you use the reverse option, the for loop subtracts the step from loop_counter. 1) record. The for loop can be used effectively and conveniently as per our necessity to loop around or execute certain statements repetitively. A special flag "auto-held" marks > such cursors, so we know to clean them up on exceptions. Declaring Cursor Variables. Besides this, even the result set retrieved from a particular query can be iterated using for loop in PostgreSQL. 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: ; Second, the from and to are expressions that specify the lower and upper bound of the range. > 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? 40.7.1. GitHub Gist: instantly share code, notes, and snippets. By default, the for loop adds the step to the loop_counter after each iteration. As of PostgreSQL 7.1.x, cursors may only be defined as READ ONLY, and the FOR clause is therefore superfluous. 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. Hopefully the … For prior versions, you need to create a function and select it. Example. AFAICS it'd be exactly the same. Might as well stick with the simpler notation. PostgreSQL cursor example. Recommended Articles. I remember being advised against cursors once SQL 6.5 came out and finally got rid of them once we had table variables. This is a guide to PostgreSQL For Loop. Declaring Cursor Variables. 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: In this syntax: First, the for loop creates an integer variable loop_counter which is accessible inside the loop only. It means that you can only reference it inside the loop, not outside. 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. 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. Direct cursor support is new in PL/pgSQL version 7.2. > As alluded to in earlier threads, this is done by converting such > cursors to holdable automatically. The record variable is local to the cursor FOR LOOP statement. 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. 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. 41.7.1. Example 7-42. After the cursor FOR LOOP statement execution ends, the record variable becomes undefined. Doesn’t this look silly: With PostgreSQL from 9.0, you can simply drop into executing plpgsql using a "DO" block. Declaring a cursor 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.. Cursors may only be defined as READ only, and snippets of the range this, the. Got rid of them once we had table variables: First, the for loop creates an integer loop_counter... And the for loop statement used effectively and conveniently as per our necessity to loop around or execute statements! 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