CODEWITHSUNDEEP
mysqlsql
renGth
renGth

Reputation: 27

How to use SQL alias with variable

I have the following code:

set @a='city_name';
select place_names from table1 tbl1 inner join table2 tbl2 
   on tbl1.city_name = tbl2.city_name

Here I need to use variable @a with alias tbl1. Something like tbl1.@a and tbl2.@a.

How can I do this?

Thanks in advance.

Upvotes: 2

Views: 6310

Answers (1)

Bill Karwin
Bill Karwin

Reputation: 562951

Syntax, including column names and other identifiers, must be fixed at the time the statement is parsed.

The only way to use a user variable as part of SQL syntax is to use a prepared statement, so you can build a SQL statement as a string before it is parsed.

SET @a='city_name';

SET @sql=CONCAT('select place_names from table1 tbl1 inner join table2 tbl2 
   on tbl1.', @a, ' = tbl2.', @a);

PREPARE stmt1 FROM @sql;
EXECUTE stmt;

Upvotes: 3

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