SQL Server performs sort, intersect, union, and difference operations using in-memory sorting and hash join technology. Using this type of query plan, SQL Server supports vertical table partitioning, sometimes called columnar storage.
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...
SELECTcustomer_nameFROMcustomersWHEREcustomer_idIN(SELECTcustomer_idFROMtransactionsWHEREamount>1000);--...
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 优雅处理数据插入、更新时主键或者唯一键冲突...
SELECTcolumn_name(s)FROMtable_nameWHEREEXISTS(SELECT1FROManother_tableWHEREcondition); 1. 2. 3. 4. 5. 6. 7. SELECT 1:在 EXISTS 的子查询中,通常使用SELECT 1或其他任何常量,因为 EXISTS 只关心是否返回了行,而不关心实际返回了什么值。
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 ...
SELECT Customers.CompanyFROM Customers LEFT JOIN Orders ON Customers.ID = Orders.[Customer ID] WHERE (((Orders.[Order ID]) Is Null)) Query Results Run the query, and you see only the companies who have no associated orders: Finding Records that Exist in One Table, but Not in a Query ...
The SELECT INTO statement copies data from one table into a new table.SELECT INTO SyntaxCopy all columns into a new table:SELECT * INTO newtable [IN externaldb] FROM oldtableWHERE condition; Copy only some columns into a new table:
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...
SELECTcolumn1, column2, column3, ...INTOdestination_tableFROMsource_table; Here, column1, column2, column3, ...are the columns to be copied destination_tableis the new table where the data is to be copied to source_tableis the table where the data is to be copied from ...