How to cast and update a numeric value from string column only where applicable in MySQL?

You can use the CEIL() function from MySQL. Let us first create a table. Here, we have taken the first column as VARCHAR −

mysql> create table DemoTable
   -> (
   -> Value varchar(20),
   -> UpdateValue int
   -> );
Query OK, 0 rows affected (1.08 sec)

Insert some records in the table using insert command −

mysql> insert into DemoTable(Value) values('100');
Query OK, 1 row affected (0.11 sec)
mysql> insert into DemoTable(Value) values('false');
Query OK, 1 row affected (0.10 sec)
mysql> insert into DemoTable(Value) values('true');
Query OK, 1 row affected (0.07 sec)
mysql> insert into DemoTable(Value) values('1');
Query OK, 1 row affected (0.07 sec)

Display all records from the table using select statement −

mysql> select *from DemoTable;

This will produce the following output −

+-------+-------------+
| Value | UpdateValue |
+-------+-------------+
|   100 |        NULL |
| false |        NULL |
|  true |        NULL |
|     1 |        NULL |
+-------+-------------+
4 rows in set (0.00 sec)

Following is the query to cast and update a numeric value from string column only where applicable −

mysql> update DemoTable
   -> set UpdateValue=ceil(cast(Value AS char(7)));
Query OK, 4 rows affected (0.18 sec)
Rows matched: 4 Changed: 4 Warnings: 0

Let us check the table records once again −

mysql> select *from DemoTable;

This will produce the following output −

+-------+-------------+
| Value | UpdateValue |
+-------+-------------+
|   100 |         100 |
| false |           0 |
|  true |           0 |
|     1 |           1 |
+-------+-------------+
4 rows in set (0.00 sec)