2.2 使用关联子查询 SELECTcolumn1,column2,...FROMtable1,(SELECTcolumn1,column2,...FROMtable2WHEREcondition)ASsubqueryWHEREtable1.column1=subquery.column1; 1. 2. 3. 或者 SELECTcolumn1,column2,...FROMtable1INNERJOIN(SELECTcolumn1,column2,...FROMtable2WHEREcondition)ASsubqueryONtable1.column1=...
各个SELECT语句之间使用UNION或UNION ALL关键字分隔。 语法格式: SELECT column,... FROM table1 UNION [ALL] SELECT column,... FROM table2 UNION操作符 UNION 操作符返回两个查询的结果集的并集,去除重复记录。 UNION ALL操作符 UNION ALL操作符返回两个查询的结果集的并集。对于两个结果集的重复部分,不...
标量子查询(scalar subquery):返回1行1列一个值 行子查询(row subquery):返回的结果集是 1 行 N 列 列子查询(column subquery):返回的结果集是 N 行 1列 表子查询(table subquery):返回的结果集是 N 行 N 列 子查询可以返回一个标量(就一个值)、一个行、一个列或一个表,这些子查询分别称之为标量...
SELECT * FROM (SELECT 1, 2, 3, 4) AS dt(col1, col2, col3, col4) #高版本mysql支持语法 1. 2. 3. A derived table can return a scalar, column, row, or table. Derived tables are subject to these restrictions: A derived table cannot be a correlated subquery. A derived table canno...
SELECT * FROM buy_log WHERE userid=2; 索引选择:优化器最终的选择是索引 userid,因为该索引的叶子节点包含单个键值,所以理论上一个页能存放的记录应该更多。情况 2: SELECT * FROM buy_log WHERE userid=1 ORDER BY buy_date DESC LIMIT 3;
The Ultimate Guide To SQL Server Subquery来个图解,w3resources.com 看看执行语句的顺序吧,感觉十分清楚~IN的基本语句结构: SELECT column-names FROM table-name1 WHERE value IN (SELECT column-name FROM table-name2 WHERE condition) ANY 的基本语句结构: SELECT column-names...
select distinct vend_id from products; # 使用distinct关键字去重,distinc只能放在列名的前面 select distinct vend_id,prod_price from products; # distinct不仅对前置它的列vend_id起作用,同时也作用于prod_price,两列值有重复,才去重 limt关键字 限制返回结果的数量和查询的范围,行数下标从0开始 ...
select id, name, (select count(tableB.id) from tableB where tableB.id_tableA = tableA.id) as haveBonA, (select count(tableC.id) from tableC where tableC.id_tableA = tableA.id) as haveConA, IF(haveBonA=haveConA,"Equal","Not Equal") AS equalTableBTableC from ...
SELECT id, name FROM emp WHERE salary = (SELECT MIN(salary) FROM emp GROUP BY department_id); -- 错误:Subquery returns more than 1 row 多行子查询使用单行比较符 3. 多行子查询 也称为集合比较子查询 内查询返回多行 使用多行比较操作符 3.1 多行比较操作符 体会ANY 和 ALL 的区别 3.2 代码...
SELECT[Id],[Name],[Price],[CreateTime],[CustomId]FROM[Order]WHERE( ([Name]like'%'+CAST(@MethodConst0ASNVARCHAR(MAX))+'%')OR([Name]like'%'+CAST(@MethodConst1ASNVARCHAR(MAX))+'%') ) Feature5 : Multi-tenant transaction //Creaate database objectSqlSugarClient db =newSqlSugarClient(ne...