SQL还可以在一个SELECT语句或UPDATE语句中,表达与面向过程语言一样非常复杂而且灵活的条件分支,不过这需要借助CASE表达式。 之所以叫它CASE“表达式”而不是CASE“语句”(statement),是因为CASE表达式与1+(2-4)或者(x*y)/z一样,都是表达式,在执行时会被整体当作一个值来处理。既然同样是表达式,那么能写1+1这样的表达式的地
问Oracle SQL在group by & select子句和CASE运算符中同时使用子查询EN下面来总计下之前的随笔中所说过...
SQL中的 CASE 类似编程语言里的 if-then-else 语句,用做逻辑判断。可以用于SELECT语句中,也可以用在WHERE,GROUP BY 和 ORDER BY 子句;可以单独使用,也可以和聚合函数结合使用。 语法如下: CASE WHEN conditi…
SQLGROUP BYStatement ❮ PreviousNext ❯ TheGROUP BYstatement groups rows that have the same values into summary rows, like "find the number of customers in each country". TheGROUP BYstatement is often used with aggregate functions (COUNT(),MAX(),MIN(),SUM(),AVG()) to group the result...
1topics: #CASE的两种基本用法2CASE OPERATOR3CASE STATEMENT45MariaDB [mysql]> helpcasestatement; #case的第一种用法6Name: 'CASE STATEMENT'7Description:8Syntax:9CASE case_value10WHEN when_value THEN statement_list11[WHEN when_value THEN statement_list] ...12[ELSE statement_list]13END CASE1415Or...
SQL 中Group By语句大家都很熟悉,根据指定的规则对数据进行分组,常常和聚合函数一起使用。 比如,考虑有表dealer,表中数据如下: 如果执行 SQL 语句SELECT id, sum(quantity) FROM dealer GROUP BY id ORDER BY id,会得到如下结果: 代码语言:javascript
The GROUP BY clause comes to the rescue, specifying that the SUM function has to be executed for each unique CustomerName value. In this case the GROUP BY clause acts similar to DISTINCT statement, but for the purpose of using it along with SQL aggregate functions. The result set retrieved...
Knowing which of the columns you want to group by and how you want to group them, first, is important. You will need to know that to set up theCASE STATEMENTwe’re going to write as a column in a our select statement. In our case, in a group of emails that are accessing our sit...
CASE表达式是用来判断条件的,条件成立时返回某个值,条件不成立时返回另一个值。 语法: CASEWHENComparsionConditionTHENresultWHENComparsionConditionTHENresultELSEotherEND (注:各分支返回的数据类型需一致。) (注:when子句一定要有排他性,因为当when子句为真时,剩余的when子句会被忽略。) ...
sql_statement_recompile扩展事件 (XEvent) 报告语句级重新编译。 当任何类型的批处理需要语句级重新编译时,会发生此 XEvent。 这包括存储过程、触发器、即席批处理和查询。 可通过几个接口来提交批处理,这类接口包括 sp_executesql、动态 SQL、“准备”方法或“执行”方法。