What is wrong with the syntax of this MySQL query on dates?

Question

phpMyAdmin tells me that the following code snippet is syntactically incorrect :

 SET @time := NOW();
 SET @timeset :=0;


 IF @timeset=1 
    THEN SET @time := DATE_ADD(@time,INTERVAL 10 SECOND);
    ELSE SET @time := DATE_SUB(NOW(),INTERVAL 1 DAY);
         SET @timeset := 1; 
    END IF; 

but I fail to see what's wrong with it.

The exact error message goes :

UPDATE : thanks to wolfgangalther's answer, I found the following workaround :

SET @time := NOW();
SET @timeset :=0;
SET @time=IF(@timeset=1,DATE_ADD(@time,INTERVAL 10 SECOND),DATE_SUB(NOW(),INTERVAL 1 DAY)); 
SET @timeset:=1; 

Answer 1

From the MySQL manual :

MySQL supports the IF, CASE, ITERATE, LEAVE LOOP, WHILE, and REPEAT constructs for flow control within stored programs .

You are not allowed to issue an IF construct on its own!

There is also a short discussion about it here (including some alternatives): https://dba.stackexchange.com/questions/80132/using-if-statement-outside-of-a-stored-procedure-or-function

Note: Using an IF statement at that place has been requested as a feature in the past , but is not implemented into MySQL as of now.

Edit:
Stored programs are either stored procedures or stored functions. Stored functions are the same thing as stored procedures, they just return a value.

Read more about stored procedures:

• Stackoverflow: What is a stored procedure?
• Tutorial: An Introduction to Stored Procedures in MySQL 5
• MySQL manual: Stored Programs and Views

Answer 2

This kind of IF ELSE you can only use in stored procedures, But you can use If condition in query as given below.

IF(expr,if_true_expr,if_false_expr)

Example

SELECT customerNumber,
       customerName,
       IF(state IS NULL,'N/A',state) state,
       country
FROM customers;