Fetching and updating cursors


26-Mar-2020 10:27

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So this means if you use "CURRENT OF", it is an update on the specified cursor, and with static cursor (which is read-only), we will get the error you posted.However, when you are not using "CURRENT OF", you are doing the update on the underlying table directly, which in such case has nothing to do with the specified cursor, thus it does not matter whether the cursor is Read Only or NOT.Since Row 4, (2002040, Sam, Burke) was fetched after “Sam” was updated to “Joe,” the returned employee ID 2002040 is Joe, Burke.

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Summary: in this tutorial, we will show you how to use PL/pg SQL Cursor and give you some practical examples of using cursors.DECLARE @nome varchar(100), @salario int,@idemp int DECLARE contact_cursor CURSOR STATIC FOR SELECT empno,ename, sal FROM emp OPEN contact_cursor; FETCH NEXT from contact_cursor into @idemp,@nome, @salario WHILE @@FETCH_STATUS=0 BEGIN CURRENT OF Specifies that the update is performed at the current position of the specified cursor.A positioned update using a WHERE CURRENT OF clause updates the single row at the current position of the cursor.Scan count 1, logical reads 2 Table '##Cursor Test'. Scan count 1, logical reads 2 Table '##Cursor Test'. Scan count 0, logical reads 2 Table '##Cursor Test'. Scan count 1, logical reads 2 Table '##Cursor Test'. Scan count 0, logical reads 2 Table '##Cursor Test'. Scan count 1, logical reads 2 Table '##Cursor Test'. Scan count 0, logical reads 2 Table '##Cursor Test'. Scan count 1, logical reads 2 Table '##Cursor Test'. Scan count 0, logical reads 2 Table '##Cursor Test'. Scan count 1, logical reads 2 UPDATE ##Cursor Test SET [Val] = 1; SELECT * FROM ##Cursor Test; SET STATISTICS IO ON; DECLARE cur Test CURSOR TYPE_WARNING LOCAL FORWARD_ONLY STATIC OPTIMISTIC FOR SELECT [ID] FROM ##Cursor Test WHERE [Val] Table 'Worktable'.

Scan count 0, logical reads 8 Table '##Cursor Test'. Scan count 0, logical reads 2 Table '##Cursor Test'. Scan count 0, logical reads 2 Table '##Cursor Test'. Scan count 0, logical reads 2 Table '##Cursor Test'. Scan count 0, logical reads 2 Table '##Cursor Test'. Scan count 0, logical reads 2 being the better option, and a more complicated query for the Cursor might be an even bigger difference (assuming you are able to update based on the Clustered Key of the target table).If we process it at once, we may have a memory overflow error.