While SQL While loop is quicker than a cursor, reason found that cursor is defined by DECLARE CURSOR. Every emphasis of the loop will be executed inside system memory and consuming required server assets. On the off chance that the iteration count is extremely high, at ...
Again, it really depends on your situation. I almost always use a cursor to loop through records...
CURSOR FOR Loop FOR employee_rec in c1 ---employee_rec直接用,不用提前定义 LOOP total_val := total_val + employee_rec.monthly_income; END LOOP; 当使用CURSOR FOR Loop时,不用我手工open cursor close cursor 应用: begin FOR emm IN ( SELECT ro_site, ns_site, product_line, wh_type FROM ...
declare--存储域名type t_curisrefcursor; domainNames t_cur; domainNamevarchar2(50) :='';--存储每个域下的网元类型cursormoTypeNames(domainVARCHAR2)ISselectt1.modelnamefrompm4h_mo.mdl_resmodel t1,pm4h_mo.mdl_domain t2wheret2.domainname=domainandt1.domainid=t2.domainid; moTypeNamevarchar2(500...
The WHILE loop, according toSQL Server Loop through Table Rows without Cursorarticle, states that a WHILE is faster than a cursor and uses less locks and use less TEMPDB resources. However, WHILE loops are still slow and have a performance impact. If it is a nested loop, it will be even...
游标Cursor逻辑运算符和物理运算符用于描述涉及游标操作的查询或更新的执行方式。 其中物理运算符描述用于处理游标(如使用键集驱动游标)的物理实现算法。 游标执行过程的每一步都涉及物理运算符。 而逻辑运算符描述游标的属性,如游标是只读。 逻辑运算符包括Asynchronous、Optimistic、Primary、Read Only、Scroll Locks、...
Often, cursors are used to perform a function row by row. If there is a primary key on a table, you can usually write a WHILE loop to do the same work without incurring the overhead of a cursor. The following example is very simple but demonstrates this approach:code Copy ...
cursor%ROWTYPE; begin open student_cursor; loop fetch student_cursor INTO student_row; exit when student_cursor%NOTFOUND; dbms_output.put_line( student_row.SNO || '' || student_row.SNAME|| '' || student_row.CNAME || '' || student_row.DEGREE); end loop; close student_cursor; END...
原文:从使用者,DBA,内核开发三个不同角度来分析SQL的性能优化原理 有时候写的SQL有性能问题时往往束手无策,而求助于DBA。 今天,我们从使用者、DBA、内核开发三个不同的角度来分析一个有趣的SQL性能问题的案例, 从浅入深了解的优化原理。 问题描述 同事A来问我这个假DBA一条SQL的性能问题: A:两条SQL语句只...
You are fetching the next record outside the WHILE loop using the above code. So the @@FETCH_STATUS is always 0 and the loop is executed infinitely. Place the above statement inside the WHILE loop. For more details refer below article....