SQL Operator Precedence.

Logical Operator has Precedence and here is the ranking:

  • Operator precedence describes the order in which operations are performed when an expression is evaluated.
  • Operations with a higher precedence are performed before those with a lower precedence.
  • Parentheses has the highest precedence and OR has the lowest.
MySQL, Oracle, SQL server, PostgreSQL:
select ISBN_no "ISBN",
       item_qty*PRICE "Order Sum" 
  from order_books
  where Isbn_no like '%8'
  OR Isbn_no like '0%'
  AND item_qty*PRICE < 100
This will give you:
Find Isbn number and order total for all orders where Isbn_no ends with the letter of 8 or where Isbn number starts with the letter 8 and has an order amount less than $ 100.
The result should be:
ISBN Order Sum
0201703092 78
0764557599 42
0672325764 49
0764557599 84
0764579088 140
0471777781 64
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