SQL Server performs sort, intersect, union, and difference operations using in-memory sorting and h...
一种常用的方法是使用NOT IN子句来实现从一个表中选择所有在另一个表中不存在的记录。NOT IN子句可以用来在条件语句中排除一个集合中的值。具体的语法如下: SELECTcolumn_name(s)FROMtable1WHEREcolumn_nameNOTIN(SELECTcolumn_nameFROMtable2); SQL Copy 在上面的语法中,table1是我们要选择...
然后,我们使用子查询来选择在”customers”表中存在但在”orders”表中不存在的值。我们可以使用NOT IN关键字来达到目的。具体的SQL语句如下所示:SELECT customer_id FROM customers WHERE customer_id NOT IN (SELECT customer_id FROM orders); SQL Copy这个查询将返回在”customers”表中存在但在”orders”表中...
SELECT column_name FROM table_name WHERE column_name NOT IN (SELECT column_name FROM another_table) 注意,"NOT IN"操作符在使用时需要确保子查询的结果集不包含NULL值,否则可能导致不符合预期的结果。 "NOT EXISTS": "NOT EXISTS"操作符用于判断子查询的结果集是否为空,如果为空,则返回真(True)。它通...
WITH s1 AS ( SELECT * FROM students WHERE score > 80 ), s2 AS ( SELECT * FROM students WHERE class = 2 ) SELECT * FROM s1 WHERE s1.id NOT IN ( SELECT s2.id FROM s2 ) AND s1.grade = 'A'; 结果如下:WITH AS是从MySql 8.0.1开始提供 ...
SELECTstor_id,qtyFROM(SELECTstor_id,qtyFROMsalesWHEREqty>50)AStemp_table;2、UNION UNION运算符从...
DELIMITER // CREATE PROCEDURE my_procedure (IN param1 INT, OUT result INT) BEGIN -- 存储过程的SQL语句SELECT column1 INTO result FROM my_table WHERE another_column = param1; END // DELIMITER ; 在上述示例中: my_procedure 是存储过程的名称。 (IN param1 INT, OUT result INT) 定义了输入参数...
SELECTcolumn(列名), another_column, … FROMmytable(表名) 2、条件查询-SELECT WHERE 2.1 适用于数字类型的属性 为了更精确的查询出特定数据:SELECT查询的WHERE子句. 一个查询的WHERE子句用来描述哪些行应该进入结果,具体就是通过 condition条件 限定这些行的属性满足某些具体条件 ...
So far we have used the select statement to retrieve all the records in a table regardless if some values repeat or not. If you wish, you can use the DISTINCT keyword to remove duplicates from your results. For instance if you wanted to just return a unique list of employees’ titles yo...
SELECT TOP 5 a.BusinessEntityID, a.Rate INTO #tempTop5Paychecks -- dump to temporary table FROM HumanResources.EmployeePayHistory a INNER JOIN HumanResources.Employee b ON a.BusinessEntityID = b.BusinessEntityID WHERE b.OrganizationNode.GetLevel() > 1 -- do not include executives or C leve...