Using the value of an alias inside the same MySQL SELECT statement


You cannot directly use an alias in the SELECT. Instead, use a user-defined variable. Following is the syntax. Here, @yourAliasName is our variable and alias −

select @yourAliasName :=curdate() as anyAliasName,concat(‘yourValue.',yourColumnName,' yourValue',@yourAliasName) as anyAliasName from yourTableName;

Let us first create a table −

mysql> create table DemoTable
(
   Name varchar(40)
);
Query OK, 0 rows affected (0.62 sec)

Insert some records in the table using insert command −

mysql> insert into DemoTable values('John Smith');
Query OK, 1 row affected (0.16 sec)
mysql> insert into DemoTable values('Chris Brown');
Query OK, 1 row affected (0.16 sec)
mysql> insert into DemoTable values('David Miller');
Query OK, 1 row affected (0.12 sec)
mysql> insert into DemoTable values('John Doe');
Query OK, 1 row affected (0.18 sec)

Display all records from the table using select statement −

mysql> select *from DemoTable;

This will produce the following output −

+--------------+
| Name         |
+--------------+
| John Smith   |
| Chris Brown  |
| David Miller |
| John Doe     |
+--------------+
4 rows in set (0.00 sec)

Following is the query to use the value of an alias inside the same SQL statement −

mysql> select @todayDate :=curdate() as todayDate,concat('Mr.',Name,' The current Date is=',@todayDate) as Result from DemoTable;

This will produce the following output −

+------------+------------------------------------------------+
| todayDate  | Result                                         |
+------------+------------------------------------------------+
| 2019-09-08 | Mr.John Smith The current Date is=2019-09-08   |
| 2019-09-08 | Mr.Chris Brown The current Date is=2019-09-08  |
| 2019-09-08 | Mr.David Miller The current Date is=2019-09-08 |
| 2019-09-08 | Mr.John Doe The current Date is=2019-09-08     |
+------------+------------------------------------------------+
4 rows in set (0.00 sec)
raja
Published on 07-Oct-2019 16:07:02
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