Data Query Language

The SQL SELECT Statement

The SELECT statement is used to retrieve data from a database.

The data returned is stored in a result table, called the result-set.

Basic Syntax:

SELECT column1,column2 FROM table_name 
column1 , column2: names of the fields of the table
table_name: from where we want to fetch

Demo Database

Below is a selection from the "Consumer" table in a sample database:

SELECT Column

The following SQL statement selects the "Customer Name" and "City" columns from the "Consumer" table:

SELECT CustomerName, City FROM Consumer;

SELECT *

The following SQL statement selects all the columns from the "Consumer" table:

SELECT * FROM Consumer;

SQL Order of Execution

The SQL order of execution defines the order in which the clauses of a query are evaluated. Some of the most common query challenges I run into could be easily avoided with a clearer understanding of the SQL order of execution, sometimes called the order of operations. Understanding query order can help you diagnose why a query won't run, and even more frequently will help you optimize your queries to run faster. In today's modern world, SQL query planners can do all sorts of tricks to make queries run more efficiently, but they must always reach the same final answer as a query that is executed per the standard order of execution. This order is: