Thanks! Andrew Subject Written By Posted where in multiple columns andrew niesen September 06, 2004 05:11PM Re: where in multiple columns Nick Roper September 07, 2004 02:20AM Sorry, you can't reply to this topic. It has been closed....
•mysql-filtering-by-multiple-columns[1] •selecting-where-two-columns-are-in-a-set[2] 外部链接 [1]mysql-filtering-by-multiple-columnshttps://www.tutorialspoint.com/mysql-filtering-by-multiple-columns [2]selecting-where-two-columns-are-in-a-sethttps://db...
insert into t_demo(name,score) values('e',60); 多列in查询 代码语言:txt AI代码解释 select * from t_demo where (name,score) in (('c',30),('e',60)); +---+---+---+ | id | name | score | +---+---+---+ | 3 | c | 30 | | 6 | e | 60 | +---+---+---...
+---+ 2 rows in set Time: 0.119s 小结多列组合查询平常比较少见...doc • mysql-filtering-by-multiple-columns[1] • selecting-where-two-columns-are-in-a-set[2] 外部链接 [1]...mysql-filtering-by-multiple-columns https://www.tutorialspoint.com/mysql-filtering-by-multiple-columns 4.8K...
何为多列组合查询呢,就是查询的值不再是单个列的值,而是组合列的值。比如where (column1,column2) in ((a1,b1),(a2,b2),(a3,b3)) 实例 建表 create table t_demo( id int NOT NULL AUTO_INCREMENT PRIMARY KEY, name varchar(10), score int ...
InnoDB handlesSELECT COUNT(*)andSELECT 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 example: ...
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第二次,你删除掉表id 的主键属性,然后重新修改表以加约束主键id,然后只执行最后这一句语句会报错的,提示Multiple primary key 4,使用MySQL执行update或者delete的时候报错: 例如执行:①delete from Address; (Address 是一张表) 或者 执行:②delete from Address where StuName='赵丽颖'; 执行①②都会报错!: ...
第二次,你删除掉表id 的主键属性,然后重新修改表以加约束主键id,然后只执行最后这一句语句会报错的,提示Multiple primary key 4,使用MySQL执行update或者delete的时候报错: 例如执行:①delete from Address; (Address 是一张表) 或者 执行:②delete from Address where StuName='赵丽颖'; 执行①②都会报错!: ...
MySQL can use multiple-column indexes for queries that test all the columns in the index, or queries that test just the first column, the first two columns, the first three columns, and so on. If you specify the columns in the right order in the index definition, a single composite inde...