A select statement in SQL may contain one or more conditions (also known as predicates) in the where clause. A condition evaluates to true or false or unknown. The where clause must return a true value for a particular row to be selected.
You might wish to select all the columns in each row of a table in your SQL select statement. The syntax for accomplishing this task is straightforward because it does not require itemizing each column defined for the table.
When you run a select statement the records, or rows, that are displayed are not guaranteed to be in a specific order. Usually, you will want to sort the records to make the report more meaningful. You will learn how to sort records in this topic.
A subquery is select statement contained within an outer select statement. Two types of subqueries are available in SQL: the simple subquery and the correlated subquery. In this topic you will learn how to write each type of subquery.