Re: CASE and IF in WHERE clause 4717 m z May 20, 2009 11:38AM Re: CASE and IF in WHERE clause 7481 Peter Brawley May 20, 2009 11:57AM Re: CASE and IF in WHERE clause 4850 m z May 22, 2009 02:48PM Sorry, you can't reply to this topic. It has been closed.Content rep...
You can use one or more tables separated by a comma to include various conditions using a WHERE clause, but the WHERE clause is an optional part of the SELECT command. 您可以使用WHERE子句来使用一个或多个用逗号分隔的表来包含各种条件,但是WHERE子句是SELECT命令的可选部分。 You can specify any ...
则出现mysqlUnknowncolumn'op_task.task_no'in'whereclause'找不到这个task_no字段的错误 mysql版本为5.6,查出表A,所有数据,当表A的task_type=1时,统计表B中task_no和表A的task_no相同的数量,否则统计表C中task_no和表A的task_no相同的数量, 表A为: CREATETABLE`op_task`( idint(10)unsignedNOTNULLAUTO...
You use the simple CASE statement to check the value of an expression against a set of unique values. The case_expressioncan be any valid expression. The case_expression is compared with when_expression in each WHEN clause e.g., when_expression_1 and when_expression_2 . If the values of...
方法二三,性能相当,if性能稍快于case(可能受网络影响),都比第一种快了一倍,第一种因为两个子查询耗时。 14. 重命名不能出现在where后面吗? (下面会报Unknown column 'c' in 'where clause') https://leetcode-cn.com/problems/consecutive-numbers/ ...
We compare the value of the case_expression with when_expression in each WHEN clause e.g., when_expression_1, when_expression_2, etc. If the value of the case_expression and when_expression_n are equal, the commands in the corresponding WHEN branch executes. In case none of the when_...
UPDATE table_name SET field1=new-value1, field2=new-value2 [WHERE Clause] # 把李四的地址改为上海(默认Beijing) Update employee set city = 'Shanghai' where id = 2; 2. 更改表格 在表employee增加一列addr Alter table employee add colunm addr varchar(40); 更新表名 Rename Table 表名 to 新...
In this case, theWHEREclause rejects the row whetherIN (subquery)returnsNULLorFALSE. When either or both of those conditions do not hold, optimization is more complex. Suppose thatouter_expris known to be a non-NULLvalue but the subquery does not produce a row such thatouter_expr=inner_exp...
InnoDB handles SELECT COUNT(*) and SELECT COUNT(1) operations in the same way. There is no performance difference. For MyISAM tables, COUNT(*) is optimized to return very quickly if the SELECT retrieves from one table, no other columns are retrieved, and there is no WHERE clause. For...
Re: CASE and IF in WHERE clause 4717 m z May 20, 2009 11:38AM Re: CASE and IF in WHERE clause 7491 Peter Brawley May 20, 2009 11:57AM Re: CASE and IF in WHERE clause 4850 m z May 22, 2009 02:48PM Sorry, you can't reply to this topic. It has been closed. ...