MySQL Syntax error - mysql

Question

I am unable to run a simple script in MySQL. I have reduced the script to just one line.
DELIMITER $$
DECLARE varLocalityName VARCHAR(50);
$$
DELIMITER ;
The error is:
ERROR 1064 (42000) at line 2: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'DECLARE varLocalityName VARCHAR(50)' at line 1
$ mysql --version
mysql Ver 14.14 Distrib 5.1.63, for debian-linux-gnu (x86_64) using readline 6.2

Answer 1

Your code block does not define the scope for the declared variables. If within a procedure, they must be between BEGIN and END. Without them, the statement DECLARE varLocalityName VARCHAR(50); becomes an invalid statement to be executed. This statement is equivalent to the statements shown below:
mysql> select current_date();
+----------------+
| current_date() |
+----------------+
| 2012-10-22 |
+----------------+
1 row in set (0.00 sec)
mysql> declare varLocalityName varchar(50);
ERROR 1064 (42000): You have an error in your SQL syntax;
check the manual that corresponds to your MySQL server version
for the right syntax to use near 'declare varLocalityName varchar(50)' at line 1
mysql>
Either you should declare session variables without keyword DECLARE or follow a syntax defined for a stored procedure to use scoped variables.
Example 1: Using session variables:
mysql> set #x = null;
Query OK, 0 rows affected (0.00 sec)
mysql> select #x;
+------+
| #x |
+------+
| NULL |
+------+
1 row in set (0.00 sec)
mysql> delimiter $$
mysql> select current_date() into #x;
-> $$
Query OK, 1 row affected (0.02 sec)
mysql> select #x;
-> $$
+------------+
| #x |
+------------+
| 2012-10-22 |
+------------+
1 row in set (0.00 sec)
Note that you can set/define session variables within a procedure but not DECLARE.
Example 2: Using procedure scoped variables:
mysql>
mysql> delimiter $$
mysql> create procedure some_x()
-> begin
-> declare varLocalityName varchar(50);
->
-> set #sessionDate = null;
-> select #sessionDate;
-> set #sessionDate = current_date();
-> select #sessionDate;
->
-> select varLocalityName;
-> end;
-> $$
Query OK, 0 rows affected (0.00 sec)
mysql> delimiter ;
mysql>
mysql> call some_x();
+--------------+
| #sessionDate |
+--------------+
| NULL |
+--------------+
1 row in set (0.00 sec)
+--------------+
| #sessionDate |
+--------------+
| 2012-10-22 |
+--------------+
1 row in set (0.00 sec)
+-----------------+
| varLocalityName |
+-----------------+
| NULL |
+-----------------+
1 row in set (0.00 sec)
Query OK, 0 rows affected (0.00 sec)
mysql>
mysql> select #sessionDate;
+--------------+
| #sessionDate |
+--------------+
| 2012-10-22 |
+--------------+
1 row in set (0.00 sec)
mysql> select varLocalityName;
ERROR 1054 (42S22): Unknown column 'varLocalityName' in 'field list'
mysql>
Also refer to Variables declaration and scope.

Answer 2

I think the problem is that you define $$ as delimiter and then you still try to use ; as the delimiter
I believe this should work:
DELIMITER $$
DECLARE varLocalityName VARCHAR(50)$$
DELIMITER ;
As default MySQL delimiter is ;. You can change it with DELIMITER call and you must use it in the new syntax from then on.
DELIMITER $$
DECLARE varLocalityName VARCHAR(50)$$
SET varLocalityName="xx"$$
SELECT varLocalityName$$
DELIMITER ;
So basically $$ replaces every occurrence of ; (as long as it is not inside the String). If you set DELIMITER **, you would use double stars instead of ;.