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MySQL Mass Update with CASE WHEN/ THEN/ ELSE?
The syntax for mass update with CASE WHEN/ THEN/ ELSE is as follows −
UPDATE yourTableName set yourColumnName=case when yourColumnName=Value1 then anyUpdatedValue1 when yourColumnName=Value2 then anyUpdatedValue2 when yourColumnName=Value3 then anyUpdatedValue3 when yourColumnName=Value4 then anyUpdatedValue4 else yourColumnName end;
To understand the above syntax, let us first create a table. The query to create a table is as follows −
mysql> create table CaseUpdateDemo -> ( -> Id int, -> Name varchar(100) -> ); Query OK, 0 rows affected (0.78 sec)
Insert some records in the table using insert command. The query is as follows −
mysql> insert into CaseUpdateDemo values(1,'John'); Query OK, 1 row affected (0.17 sec) mysql> insert into CaseUpdateDemo values(2,'Carol'); Query OK, 1 row affected (0.27 sec) mysql> insert into CaseUpdateDemo values(3,'Mike'); Query OK, 1 row affected (0.11 sec) mysql> insert into CaseUpdateDemo values(4,'Bob'); Query OK, 1 row affected (0.15 sec)
Display all records from the table using select statement. The query is as follows −
mysql> select *from CaseUpdateDemo;
Output
+------+-------+ | Id | Name | +------+-------+ | 1 | John | | 2 | Carol | | 3 | Mike | | 4 | Bob | +------+-------+ 4 rows in set (0.00 sec)
Now you can write the query we discussed above to update column id with Case WHEN THEN ELSE. The query is as follows −
mysql> update CaseUpdateDemo set Id=case when Id=1 then 1001 -> when Id=2 then 1002 -> when Id=3 then 1003 -> when Id=4 then 1004 -> else Id -> end; Query OK, 4 rows affected (0.15 sec) Rows matched: 4 Changed: 4 Warnings: 0
Now you can check whether the table is updated for ID column using select statement. The query is as follows −
mysql> select *from CaseUpdateDemo;
Output
+------+-------+ | Id | Name | +------+-------+ | 1001 | John | | 1002 | Carol | | 1003 | Mike | | 1004 | Bob | +------+-------+ 4 rows in set (0.00 sec)
Updated on: 25-Jun-2020
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