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...
SQL Server performs sort, intersect, union, and difference operations using in-memory sorting and h...
Finding Records in One table that Don't Exist in Another Table (the Not-In Query) Now assume that we ONLY want to find the customers who have not placed any orders. Just like in the first scenario, we will use a Left Outer Join to accomplish this. This time, however, we’ll add ...
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...
ALTER TABLE では、列と制約を変更、追加、または削除して、テーブルの定義を変更します。 また、ALTER TABLE では、パーティションを再割り当ておよび再構築したり、制約とトリガーを無効化および有効化したりもします。
history_table_name [, DATA_CONSISTENCY_CHECK = { ON | OFF } ] ) ] } Arguments database_name The name of the database in which the table is created. database_name must specify the name of an existing database. If not specified, database_name defaults to the current database. The...
the table hints aren't used on those tables and aren't propagated. For example, aNOLOCKtable hint is specified on a table in the query. This table has computed columns that are computed by a combination of expressions and functions that access columns in another table. The tables referenced...
The SQL NOT IN clause is used frequently, yet many DBAs don’t know how it works internally - read this blog and find out!
INSERT mytable VALUES ('Dan'); 通过优化锁定,仅当实例中至少有一个使用 RangeI-N 隔离级别的事务时,才会获取 SERIALIZABLE 锁。 RangeI-N 模式键范围锁放置在与名称 David 对应的索引行上,以测试范围。 如果已授权锁,则插入包含值 Dan 的行,并将排他 (X) 锁放置在插入的行上。 RangeI-N 模...
The SQL Editor does not have IntelliSense prompting. When editing SQL statements, certain Transact-SQL statements are enclosed in a box surrounded by a thin line. This helps to visually break the SQL code into command sections, and identifies blocks of SQL statements that can be graphically desi...