.

Similarly, how do I create a sub query in SQL?

SQL - Sub Queries

1. Subqueries must be enclosed within parentheses.
2. A subquery can have only one column in the SELECT clause, unless multiple columns are in the main query for the subquery to compare its selected columns.
3. An ORDER BY command cannot be used in a subquery, although the main query can use an ORDER BY.

Similarly, what is subquery in SQL with examples? A subquery is a query that is nested inside a SELECT , INSERT , UPDATE , or DELETE statement, or inside another subquery. A subquery can be used anywhere an expression is allowed. In this example a subquery is used as a column expression named MaxUnitPrice in a SELECT statement.

Secondly, how do you write a sub query?

Important Rule:

1. A subquery can be placed in a number of SQL clauses like WHERE clause, FROM clause, HAVING clause.
2. You can use Subquery with SELECT, UPDATE, INSERT, DELETE statements along with the operators like =, <, >, >=, <=, IN, BETWEEN, etc.
3. A subquery is a query within another query.

When should we use subquery instead of join?

Subqueries can be used to return either a scalar (single) value or a row set; whereas, joins are used to return rows. A common use for a subquery may be to calculate a summary value for use in a query. For instance we can use a subquery to help us obtain all products have a greater than average product price.