MySQL事务和变量的问题

Question

I'm trying to set up a process where my team can do some routine DB changes using variables and a basic script. I'm only on the first of many operations and can't even get it to execute. The idea is you assign the variables at the top of the script and say if you want to run the script in test or prod mode.

test should just mock the changes, show you what would've happened and roll the transaction back while prod will actually commit the transaction and show you the updated rows.

When I run these lines individually they work, but altogether it keeps saying syntax error. I would love help debugging this but also if anyone has a better solution to this problem I'm wide open to hearing it.

Ok here's the starting code, thanks in advance!

#ADD A NEW QUESTION CATEGORY
SET @new_category_name = 'NEW CATEGORY NAME HERE';
SET @prod_or_test = 'PROD';

START TRANSACTION;
#SET IT'S SORT_ORDER TO BE AT THE END OF THE LIST
SET @last_sort_order = ((SELECT MAX(`sort_order`) FROM question_categories)+1);

#INSERT THE NEW ROW
INSERT INTO question_categories (name, sort_order) VALUES (@new_category_name, @last_sort_order);
IF (@prod_or_test = 'PROD') THEN
  COMMIT;
  SELECT * FROM question_categories WHERE name = @new_category_name;
ELSE
  ROLLBACK;
END IF;

Updated to include the error messages:

[ERROR in query 6] 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 'IF (@prod_or_test = 'PROD') THEN
  COMMIT' at line 1
[ERROR in query 8] 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 'ELSE
  ROLLBACK' at line 1
[ERROR in query 9] 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 'END IF' at line 1

Answer 1

IF , THEN , ELSE and END IF are not valid SQL statements, outside of the context of a MySQL stored program . For example a PROCEDURE or a TRIGGER definition.

Reference: https://dev.mysql.com/doc/refman/5.7/en/if.html

The IF statement can be used in stored programs, but it can't be used as a standalone SQL statement.

Also, the IF statement shouldn't be confused with the IF() function, which can be used in the context of a statement such as a SELECT or UPDATE , which are valid SQL statements.

  SELECT t.foo, IF(t.foo='bar',41,NULL) AS bar, ...   

Some statements include the IF keyword as part of their syntax, for example:

  DROP TABLE IF EXISTS foo; 

Note that in this example, the IF keyword is part of a DROP statement; it's not a separate statement.

---

FOLLOWUP

" the end goal was to have one script ... but ... it's looking like I actually am trying to have some stored procedures that can be called via this script. "

The original answer (above) was addressing the usage of the IF statement outside of a MySQL stored program. If you need to use the IF statement, then that could be done in a PROCEDURE.

However, an IF statement isn't strictly required. You could accomplish nearly the same thing using PREPARE , EXECUTE and DEALLOCATE PREPARE statements to execute dynamically created SQL.

Reference: https://dev.mysql.com/doc/refman/5.7/en/sql-syntax-prepared-statements.html

For example, we could perform a conditional test on a user defined variable in an IF() function in a SELECT statement, and conditionally return a SQL text to execute. In this case, either a COMMIT or a ROLLBACK statement.

I think something like this would work:

 -- add a new question category
 SET @new_category_name := 'NEW CATEGORY NAME HERE';
 SET @prod_or_test := 'PROD';

 START TRANSACTION;

 -- set it's sort_order to be at the end of the list
 SELECT IFNULL(MAX(`sort_order`)+1,1) 
   FROM question_categories
   INTO @last_sort_order 
 ;

 -- insert the new row
 INSERT INTO question_categories (name, sort_order)
 VALUES (@new_category_name, @last_sort_order)
 ;

 -- conditionally execute a COMMIT or ROLLBACK
 SELECT IF(@prod_or_test='PROD','COMMIT','ROLLBACK') INTO @sql;
 PREPARE stmt FROM @sql;
 EXECUTE stmt;
 DEALLOCATE PREPARE stmt;

 SELECT *
   FROM question_categories
  WHERE @prod_or_test = 'PROD'
    AND name = @new_category_name ;

Answer 2

issue is with the brackets

IF (@prod_or_test = 'PROD') THEN

to

IF @prod_or_test = 'PROD' THEN

syntax

IF search_condition THEN statement_list
    [ELSEIF search_condition THEN statement_list] ...
    [ELSE statement_list]
END IF

https://dev.mysql.com/doc/refman/5.7/en/if.html