If you want to use the same style but make it work, you need to add your own index/row co...
If you want to use the same style but make it work, you need to add your own index/row co...
Using a different type of FOR loop, you can iterate through the results of a query and manipulate that data accordingly. The syntax is: [ <<label>> ]FORtargetINqueryLOOPstatementsENDLOOP[label]; 3.5 Looping Through Arrays The FOREACH loop iterates through the elements of an array value. Th...
方法1:使用LOOP,LOOP中使用EXIT直接退出,保证只执行一次: 1declarefound boolean :=false; 2forxin(SELECT*FROMtbl_some_tableWHEREsome_condition) loop 3found :=true; 4--Do something here; 5endloop; 6IFnotfoundTHEN 7--DO something else 8ENDIF; 为了保证执行一次:可以如下 1forxin(SELECT*FROMtbl_s...
(1) LOOP-EXIT-END循环 语法格式: LOOP Run_expression /*执行循环体*/ IF Boolean_expression THEN /*测试Boolean_expression是否符合退出条件*/ EXIT; /*满足退出条件,退出循环*/ END IF; END LOOP; declare i number; begin for i in 1..10 ...
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嵌套循环(Nested Loop):逐行匹配两个数据集 哈希连接(Hash Join):使用哈希表实现数据集连接 排序(Sort):对结果集进行排序操作 1.3 成本估算模型 数据库优化器基于以下因素估算执行成本: 表和索引的统计信息 数据分布和选择性 硬件配置(CPU、内存、磁盘)
--CREATE a table to store the results CREATE TABLE IF NOT EXISTS ordertotals (order_num INT, total DECIMAL(8,2)); --Open the cursor OPEN ordernumbers; --Loop through all rows REPEAT --GET order number FETCH ordernumbers INTO o; --Get the total for this order CALL ordertotal(o,1,...
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...
Use the Collection page of the Foreach Loop Editor dialog box to specify the enumerator type and configure the enumerator. To learn about the Foreach Loop container and how to configure it, see Foreach Loop Container and Configure a Foreach Loop Container. Static Options Enumerator Select the ...