Its a simple slide about sub-queries.

1. SQL SUBQUERY
S.M. TOWHIDUL ISLAM
181-35-2435
E

2. WHAT IS A SUBQUERY?
 A subquery is a SELECT statement embedded in a clause of another SQL statement (SELECT, INSERT,
UPDATE, DELETE).
 SQL subquery is usually added in the WHERE Clause of the SQL statement.
SELECT . . .
FROM . . .
WHERE . . .
(SELECT . . .
FROM . . .
WHERE . . .)
Main
Query
Subquery

3. SUBQUERY
 Subquery or Inner query or Nested query.
 An alternate way of returning data from multiple tables.
 Subqueries can be used with the following SQL statements along with the comparison operators like =,
<, >, >=, <= etc.
 Subqueries can also be used inside the WHERE or HAVING clause.
SELECT select_list
From table
WHERE OOP operator SELECT select_list
From table

4. SUB-QUERY SYNTAX
The subquery (inner query) executes once
before the main query.
 The result of the subquery is used by the
main query (outer query).

5. TYPES OF SUBQUERIES

6. TYPES OF SUBQUERIES
 Single-row subqueries: Queries that return only one row from the inner SELECT statement.

7. TYPES OF SUBQUERIES
 Multiple-row subqueries: Queries that return more than one row from the inner SELECT statement.

8. THANK YOU