使用另一个表中的值更新 MySQL 表?

mysqlmysqli database

我们可以借助内连接来更新另一个表。让我们创建两个表。

创建表

mysql> CREATE table tblFirst
   -> (
   -> id int,
   -> name varchar(100)
   -> );
Query OK, 0 rows affected (0.48 sec)

插入记录

mysql> INSERT into tblFirst values(1,'John');
Query OK, 1 row affected (0.17 sec)

mysql> INSERT into tblFirst values(2,'Bob');
Query OK, 1 row affected (0.26 sec)

mysql> INSERT into tblFirst values(3,'David');
Query OK, 1 row affected (0.20 sec)

显示所有记录

mysql> SELECT * from tblFirst;

以下是输出 −

+------+-------+
| id   | name  |
+------+-------+
| 1    | John  |
| 2    | Bob   |
| 3    | David |
+------+-------+
3 rows in set (0.00 sec)

创建第二个表

mysql> CREATE table UpdTable
   -> (
   -> IncId int auto_increment,
   -> primary key(IncId),
   -> id int,
   -> name varchar(100)
   -> );
Query OK, 0 rows affected (0.57 sec)

插入记录

mysql> INSERT into UpdTable(id,name) values(1,'Taylor');
Query OK, 1 row affected (0.12 sec)

mysql> INSERT into UpdTable(id,name) values(2,'jason');
Query OK, 1 row affected (0.24 sec)

mysql> INSERT into UpdTable(id,name) values(3,'carol');
Query OK, 1 row affected (0.14 sec)

mysql> INSERT into UpdTable(id,name) values(4,'john');
Query OK, 1 row affected (0.16 sec)

显示所有记录

mysql> SELECT * from UpdTable;

以下是输出 −

mysql> SELECT *from UpdTable;
+-------+------+--------+
| IncId | id   | name   |
+-------+------+--------+
| 1     | 1    | Taylor |
| 2     | 2    | jason  |
| 3     | 3    | carol  |
| 4     | 4    | john   |
+-------+------+--------+
4 rows in set (0.00 sec)

查看上面的输出，姓氏与第一个表记录匹配。现在，我将编写 UPDATE − 的查询

mysql> UPDATE UpdTable
   -> inner join tblFirst ON (UpdTable.name = tblFirst.name)
   -> SET UpdTable.id = tblFirst.id;
Query OK, 1 row affected (0.19 sec)
Rows matched: 1 Changed: 1 Warnings: 0:0

我们已将最后一条记录更新如下 −

查询是

mysql> SELECT * from UpdTable;

以下是输出 −

+-------+------+--------+
| IncId | id   | name   |
+-------+------+--------+
| 1     | 1    | Taylor |
| 2     | 2    | jason  |
| 3     | 3    | carol  |
| 4     | 1    | john   |
+-------+------+--------+
4 rows in set (0.00 sec)

查看示例输出。id 已更新，原先为 4，但现在为 1。