Why the order of evaluation for expressions involving user variables is undefined?

by

The order of evaluation of expressions in the select is undefined. For the most part, you only notice this when you have variables, because the errors result in erroneous information.

Why? The SQL standard does not require the order of evaluation, so each database is free to decide how to evaluate the expressions. Typically such decisions are left to the optimizer.

More Related Contents:

  1. Get top n records for each group of grouped results
  2. Which DB technology is sued to solve the following search issue? [closed]
  3. MySQL pivot row into dynamic number of columns
  4. Delete all Duplicate Rows except for One in MySQL? [duplicate]
  5. Count the number of occurrences of a string in a VARCHAR field?
  6. MySQL – Operand should contain 1 column(s)
  7. How to get the difference in years from two different dates?
  8. Restore table structure from frm and ibd files
  9. mysql pivot/crosstab query
  10. MySQL: Split comma separated list into multiple rows
  11. Most efficient way to get table row count
  12. UNION query with codeigniter’s active record pattern
  13. Subqueries with EXISTS vs IN – MySQL
  14. Remove Primary Key in MySQL
  15. Get most recent row for given ID
  16. Is merge statement available in MySQL
  17. Mysql covering vs composite vs column index
  18. MYSQL syntax not evaluating not equal to in presence of NULL
  19. Mysql insert random datetime in a given datetime range
  20. MySQL: LAST_INSERT_ID() returns 0
  21. MySQL UPDATE syntax with multiple tables using WHERE clause
  22. INSERT INTO or UPDATE with two conditions
  23. Insert/ Update random date in MySQL
  24. Replace null with 0 in MySQL
  25. Get total hours worked in a day mysql
  26. MySQL OPTIMIZE all tables?
  27. Strip last two characters of a column in MySQL
  28. DELETE FROM `table` AS `alias` … WHERE `alias`.`column` … why syntax error?
  29. What happens when I exhaust a bigint generated key? How to handle it?
  30. is there a length limit to group_concat or another reason why it would not work on a text field

Leave a Comment