SQL Case语句条件 是一种在SQL查询中使用的条件语句,用于根据不同的条件执行不同的操作或返回不同的结果。它类似于编程语言中的switch语句。 Case语句条件可以有多个条件和对应的操作,语法如下: 代码语言:txt 复制 CASE WHEN condition1 THEN result1 WHEN condition2 THEN result2 ... ELSE result END 其中,cond...
搜索CASE表达式:搜索CASE表达式使用一系列的条件进行比较,然后根据匹配的条件执行相应的操作。语法如下: 代码语言:txt 复制 CASE WHEN condition1 THEN result1 WHEN condition2 THEN result2 ... ELSE result END 其中,condition1、condition2等是要比较的条件,result1、result2等是匹配条件对应的结果,ELSE子句是可选...
SELECT * FROM tablename [START WITH <condition1>] CONNECT BY <condition2>; 其中START WITH子句用于指定起始条件,即<condition1>,循环关联条件为<condition2>,其中可以使用PRIOR关键字来表示来自于上一循环的列。例如上节中所述的树遍历的例子,使用Oracle的Connect By语法,语句如下: SELECT * FROM tree START...
The SQL CASE Expression TheCASEexpression goes through conditions and returns a value when the first condition is met (like an if-then-else statement). So, once a condition is true, it will stop reading and return the result. If no conditions are true, it returns the value in theELSE...
不过case when并不是专门用来做过滤的,语法使用起来也不叫复杂,也不是所有聚合函数都满足这种过滤的语意。除了case when,还有一种专门的选择性聚合算子,可以对每个聚合函数附加一个过滤条件。具体语法如: SELECT key, AGG1(x) FILTER (WHERE condition1),...
SELECT CASE WHEN condition1 THEN result1 ELSE result2 END AS condition, COUNT(1) AS count FROM table_name GROUP BY CASE WHEN condition1 THEN result1 ELSE result2 END Insert statement with CASE in SQL You can use the CASE expression to insert data into a SQL Server table. The INSERT sta...
<search_condition> 指定要在 SELECT 语句、查询表达式或子查询的结果集中返回的行的条件。对于 UPDATE 语句,指定要更新的行。对于 DELETE 语句,指定要删除的行。Transact-SQL 语句搜索条件中可以包含任意多个谓词。 NOT 对谓词指定的布尔表达式求反。有关详细信息,请参阅 NOT (Transact-SQL)。 AND 组合两个条件,...
WITH RECURSIVE integer AS ( SELECT x AS orig, x,''AS binary_text FROM GENERATE_SERIES(1000,1010) ASset(x) UNION ALL SELECT orig, FLOOR(x/2)::int, CASE WHEN x %2=1THEN'1'ELSE'0'END || binary_text FROM INTEGER WHERE x >0) ...
其中,with_query的语法为: with_query_name [ ( column_name [, ...] ) ] AS ( {select | values | insert | update | delete} ) 1. 2. 关键要点如下: 每个CTE的AS语句指定的SQL语句,必须是可以返回查询结果的语句,可以是普通的SELECT语句,也可以是INSERT、UPDATE、DELETE、VALUES等其它语句,需要通过...
The CASE statement evaluates its conditions sequentially and stops with the first condition whose condition is satisfied. In some situations, an expression is evaluated before a CASE statement receives the results of the expression as its input. Errors in evaluating these expressions are possible. Aggr...