在MySQL中交换两列的值？-mysql教程-PHP中文网

在mysql中交换两列的值？

To swap two columns, we can apply the below swapping logic.

Add both values and store them into the first column
Subtract the first column’s value from the second and store it into the second column.
Subtract the first column’s value from the updated second column and store it into the first.

The above rule structure is as follows. Suppose, the first column is a and the second column is b.

1. a = a+b;
2. b = a-b;
3. a = a-b;

Now we will apply the above rule in order to swap the two column values.

Creating a table.

mysql> create table SwappingTwoColumnsValueDemo
   -> (
   -> FirstColumnValue int,
   -> SecondColumnValue int
   -> );
Query OK, 0 rows affected (0.49 sec)

Inserting some records.

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mysql>  insert into SwappingTwoColumnsValueDemo values(10,20),(30,40),(50,60),(70,80),(90,100);
Query OK, 5 rows affected (0.19 sec)
Records: 5  Duplicates: 0  Warnings: 0

To check the column values before swapping.

mysql> select *from SwappingTwoColumnsValueDemo;

The following is the output.

+------------------+-------------------+
| FirstColumnValue | SecondColumnValue |
+------------------+-------------------+
|               10 |                20 |
|               30 |                40 |
|               50 |                60 |
|               70 |                80 |
|               90 |               100 |
+------------------+-------------------+
5 rows in set (0.00 sec)

Syntax to swap column values.

mysql> UPDATE SwappingTwoColumnsValueDemo
   -> SET FirstColumnValue = FirstColumnValue+SecondColumnValue,
   -> SecondColumnValue = FirstColumnValue-SecondColumnValue,
   -> FirstColumnValue = FirstColumnValue-SecondColumnValue;
Query OK, 5 rows affected (0.15 sec)
Rows matched: 5  Changed: 5  Warnings: 0

To check if the column values have been swapped or not.

mysql> select *from SwappingTwoColumnsValueDemo;

The following is the output.

+------------------+-------------------+
| FirstColumnValue | SecondColumnValue |
+------------------+-------------------+
|               20 |                10 |
|               40 |                30 |
|               60 |                50 |
|               80 |                70 |
|              100 |                90 |
+------------------+-------------------+
5 rows in set (0.00 sec)