在 MySQL 中，提取另一列中具有指定公共值的元组?
mysqlmysqli database更新于 2024/1/8 23:51:00
要提取具有指定公共值的元组，请使用以下语法 −
SELECT DISTINCT aliasName.yourColumnName1,aliasName.yourColumnName2,aliasName1.yourColumnName 1,aliasName1.yourColumnName2 FROM yourTableName aliasName INNER JOIN yourTableName aliasName1 ON aliasName.yourColumnName1 = aliasName1.yourColumnName1 WHERE aliasName.yourColumnName2 = 'value1' AND aliasName1.yourColumnName2 = 'value2';
为了理解上述语法，让我们创建一个表。创建表的查询如下 −
mysql> create table extractTuples -> ( -> Id int, -> Name varchar(20), -> Comments text -> ); Query OK, 0 rows affected (0.77 sec)
使用 insert 命令在表中插入一些记录。 查询语句如下 −
mysql> insert into extractTuples values(1,'John','hi'); Query OK, 1 row affected (0.20 sec) mysql> insert into extractTuples values(2,'Carol','hello'); Query OK, 1 row affected (0.17 sec) mysql> insert into extractTuples values(3,'John','Amazing'); Query OK, 1 row affected (0.13 sec) mysql> insert into extractTuples values(1,'Carol','Good'); Query OK, 1 row affected (0.14 sec)
使用 select 语句显示表中的所有记录。查询如下 −
mysql> select *from extractTuples;
输出
+------+-------+----------+ | Id | Name | Comments | +------+-------+----------+ | 1 | John | hi | | 2 | Carol | hello | | 3 | John | Amazing | | 1 | Carol | Good | +------+-------+----------+ 4 rows in set (0.00 sec)
这是提取具有指定公共值的元组的查询 −
mysql> SELECT DISTINCT tbl.Id,tbl.Name,tbl1.Id,tbl1.Name -> FROM extractTuples tbl -> INNER JOIN extractTuples tbl1 -> ON tbl.Id = tbl1.Id -> WHERE tbl.Name = 'John' AND tbl1.Name = 'Carol';
输出
+------+------+------+-------+ | Id | Name | Id | Name | +------+------+------+-------+ | 1 | John | 1 | Carol | +------+------+------+-------+ 1 row in set (0.00 sec)
