MySQL: Set user variable from result of query
Yes, but you need to move the variable assignment into the query:
SET @user := 123456;
SELECT @group := `group` FROM user WHERE user = @user;
SELECT * FROM user WHERE `group` = @group;
Test case:
CREATE TABLE user (`user` int, `group` int);
INSERT INTO user VALUES (123456, 5);
INSERT INTO user VALUES (111111, 5);
Result:
SET @user := 123456;
SELECT @group := `group` FROM user WHERE user = @user;
SELECT * FROM user WHERE `group` = @group;
+--------+-------+
| user | group |
+--------+-------+
| 123456 | 5 |
| 111111 | 5 |
+--------+-------+
2 rows in set (0.00 sec)
Note that for SET
, either =
or :=
can be used as the assignment operator. However inside other statements, the assignment operator must be :=
and not =
because =
is treated as a comparison operator in non-SET statements.
UPDATE:
Further to comments below, you may also do the following:
SET @user := 123456;
SELECT `group` FROM user LIMIT 1 INTO @group;
SELECT * FROM user WHERE `group` = @group;
Just add parenthesis around the query:
set @user = 123456;
set @group = (select GROUP from USER where User = @user);
select * from USER where GROUP = @group;
First lets take a look at how can we define a variable in mysql
To define a varible in mysql it should start with '@' like @{variable_name} and this '{variable_name}', we can replace it with our variable name.
Now, how to assign a value in a variable in mysql. For this we have many ways to do that
- Using keyword 'SET'.
Example :-
mysql > SET @a = 1;
- Without using keyword 'SET' and using ':='.
Example:-
mysql > @a:=1;
- By using 'SELECT' statement.
Example:-
mysql > select 1 into @a;
Here @a is user defined variable and 1 is going to be assigned in @a.
Now how to get or select the value of @{variable_name}.
we can use select statement like
Example :-
mysql > select @a;
it will show the output and show the value of @a.
Now how to assign a value from a table in a variable.
For this we can use two statement like :-
1.
@a := (select emp_name from employee where emp_id = 1);
select emp_name into @a from employee where emp_id = 1;
Always be careful emp_name must return single value otherwise it will throw you a error in this type statements.
refer this:- http://www.easysolutionweb.com/sql-pl-sql/how-to-assign-a-value-in-a-variable-in-mysql