A subquery can be nested inside SELECT, INSERT, UPDATE, or DELETE statements or inside another subquery. 4.How does a SQL subquery operate within a query? The inner query (subquery) executes first, and its result is passed to the outer query. This process allows the outer query to use th...
-- records with duplicate data to avaoid this we see our next example with condition SELECT * FROM Ordermasters,OrderDetails -- Simple Join with Condition now here we can see the duplicate records now has been avoided by using the where checing with both table primaryKey field SELECT * FRO...
--Sub Query -- Here we used the Sub query in where clause to get all the Item_Code where the price>40 now this sub --query reslut we used in our main query to filter all the records which Item_code from Subquery result SELECT * FROM ItemMasters WHERE Item_Code IN (SELECT Item_Co...
select_type 表示SELECT 的类型,常见的取值有 SIMPLE(简单表,即不使用表连接或者子查询)、PRIMARY(主查询,即外层的查询)、UNION(UNION 中的第二个或者后面的查询语句)、SUBQUERY(子查询中的第一个 SELECT)等 table 输出结果集的表 type 表示表的连接类型,性能由好到差的连接类型为( system ---> const --->...
Example: Using a Subquery SELECT ProductNameFROM ProductsWHERE CategoryID IN (SELECT CategoryID FROM Categories WHERE CategoryName = 'Beverages'); This query retrieves the names of products in the “Beverages” category using a subquery to find the category ID. ...
表示SELECT的类型,常见的取值,如下表所示 : SIMPLE :简单的select查询,查询中不包含子查询或者UNION PRIMARY :查询中若包含任何复杂的子查询,最外层查询标记为该标识 SUBQUERY :在SELECT或WHERE列表中包含了子查询 DERIVED :在FROM列表中包含的子查询,被标记为DERIVED(衍生)MySQL会递归执行这些子查询,把结果放在临时表...
For example, if you assume each sales person only covers one sales territory, and you want to find the customers located in the territory covered by Linda Mitchell, you can write a statement with a subquery introduced with the simple = comparison operator. SQL نسخ USE AdventureWorks20...
However, the value specified for exposed_object_name in the TABLE HINT clause must match exactly the exposed name in the query or subquery. Specify table hints as query hints We recommend using the INDEX, FORCESCAN, or FORCESEEK table hint as a query hint only in the context of...
Query hints can be specified only in the top-level query, not in subqueries. When a table hint is specified as a query hint, the hint can be specified in the top-level query or in a subquery. However, the value specified...
select_type: 查询类型simple: 简单表即不适用表连接或者子查询primary: 主查询,即外层的查询subquery: 子查询内层第一个SELECT,结果不依赖于外部查询dependent subquery: 子查询内层第一个select: 依赖于外部查询union: UNION语句中第二个SELECT开始后面所有SELECTunion result union 中合并结果DERIVED table:查询的表 ...