Can I use subquery in SELECT clause?

You can use subqueries in SELECT, INSERT, UPDATE, and DELETE statements wherever expressions are allowed. For instance, you can use a subquery as one of the column expressions in a SELECT list or as a table expression in the FROM clause.

What is a SELECT subquery?

A subquery selects and returns values to the first or outer SELECT statement. A subquery can return no value, a single value, or a set of values, as follows: If a subquery returns no value, the query does not return any rows. Such a subquery is equivalent to a null value.

How do I create a sub query in SQL Server?

How to write subqueries in SQL

1. Select clause: This clause is used to specify the resultset metadata (columns, fixed values, expressions)
2. From clause: This clause is used to specify the data sources we are querying.
3. Where clause: This clause is used to specify the data filtering operations needed in the SQL query.

When should I use a subquery?

Use subqueries when the result that you want requires more than one query and each subquery provides a subset of the table involved in the query. If a membership question is asked, then a subquery is usually used.

Which is better join or subquery?

The advantage of a join includes that it executes faster. The retrieval time of the query using joins almost always will be faster than that of a subquery. By using joins, you can maximize the calculation burden on the database i.e., instead of multiple queries using one join query.

Why do we need subquery in SQL?

A subquery is used to return data that will be used in the main query as a condition to further restrict the data to be retrieved. Subqueries can be used with the SELECT, INSERT, UPDATE, and DELETE statements along with the operators like =, <, >, >=, <=, IN, BETWEEN, etc.

How many types of subquery are there in SQL?

There are three broad divisions of subquery: Single-row subqueries. Multiple-row subqueries. Correlated subqueries.

Which is better subquery or CTE?

CTE can be more readable: Another advantage of CTE is CTE are more readable than Subqueries. Since CTE can be reusable, you can write less code using CTE than using subquery. Also, people tend to follow the logic and ideas easier in sequence than in a nested fashion.

How do you know when to use a subquery?

How many types of subqueries are there in SQL?