Data inserted or updated can be accessed with the SELECT statement of DML sublanguage of SQL.  In this tutorial you will learn to use SELECT Statement to Access Data in SQL.

Data can be fetched from more than one table. But here in this tutorial we will begin with the basic SELECT Statement. In later tutorials you will learn about its complex versions with additional clauses.

Syntax of SELECT Statement to Access Data

SELECT [DISTINCT] *|Column Name1 [alias name],Column Name2 [alias name],…

FROM table name

[WHERE condition expression]

  • SELECT, DISTINCT, FROM, WHERE are the keywords
  • *|Column Name1, Column Name2,… – defines the columns whose values must be displayed in the output of SELECT query statement. If you include * you will get data of all the columns of the table. You cannot use * and columns names together. Chose one of these two.
  • table name is the name of the table from which you want to access data.
  • Condition expression in the WHERE clause applies filter on the data being fetched from the table
  • alias name is optional. It is used to change the column heading of data being displayed

Examples of SELECT Statement

Using * to Select all Columns

select * from Salestbl;
SPID SPNAME SPCITY SPCOMM
1001 Bob Mathews Nashville .1
1002 Cathy Mills San Diego .1
1003 Alex Rode New York .5

Using Column Names to Select Data from Specific Columns

select SPCITY,    SPCOMM from Salestbl;
SPCITY SPCOMM
Nashville .1
San Diego .1
New York .5

Defining Column Aliases to Change Column Headings

If you wish to give a single word alias to column in SELECT Statement, you can simply write the word after column name as given in example below

select SPID  SalePerID, SPNAME  SalePerName, SPCITY   SalePerCIty from Salestbl;
SALEPERID SALEPERNAME SALEPERCITY
1001 Bob Mathews Nashville
1002 Cathy Mills San Diego
1003 Alex Rode New York

If you wish to give a multiple word alias with blank spaces in between the words, you have to use double quotes to enclose the alias(“”)  after column name in SELECT Statement. See the example below

select SPID  "Salesperson ID", SPNAME  "Salesperson Name", SPCITY   "Salesperson City" from Salestbl;
Salesperson ID Salesperson Name Salesperson City
1001 Bob Mathews Nashville
1002 Cathy Mills San Diego
1003 Alex Rode New York

Using Where Clause to Filter Data

select * from Salestbl where SPComm=0.1;
SPID SPNAME SPCITY SPCOMM
1001 Bob Mathews Nashville .1
1002 Cathy Mills San Diego .1

Points to remember

To use SELECT Statement to Access Data from a table remember following things

  • Selecting data from a table or set of tables do not change the data in table.
  • Using an alias name does not change the name of the column in table definition. It just changes the heading of the data.
  • Multiple conditions in WHERE clause can be added with Logical Operators AND, OR and NOT.