SQL Server Getting Started Tutorial (2): SELECT and DISTINCT statements

This chapter explains the SELECT and select * Statements and the Select DISTINCT statements.

This chapter explains the SELECT and select * Statements.

SQL SELECT Statement

The SELECT statement is used to select data from a table.

The result is stored in a result table (called a result set).

SQL Select syntax Select column name from table name

and：

SELECT * FROM table name

Note: SQL statements are not case sensitive. Select is equivalent to select.

SQL SELECT Instance

To get the contents of a column named "LastName" and "FirstName" (from a database table named "Persons"), use a SELECT statement like this:

SELECT lastname,firstname from Persons "Persons" table:

Id LastName FirstName address City 1 Adams John Oxford Street London 2 Bush George fifth Avenue New York 3 Carter Thomas Chang An street Beijing

Results:

LastName FirstName Adams John Bush George Carter Thomas

SQL SELECT * instance

Now we want to select all the columns from the Persons table.

Use the symbol * instead of the column name, like this:

SELECT * from Persons

Tip: An asterisk (*) is a shortcut to select all columns.

Results:

Id LastName FirstName Address City 1 Adams John Oxford Street London 2 Bush George fifth Avenue New York 3 Carter Thomas Changan Str EET Beijing

navigation in the result set (Result-set)

The results obtained by the SQL query program are stored in a result set. Most database software systems allow you to use programmatic functions to navigate through the result set, such as Move-to-first-record, Get-record-content, Move-to-next-record, and so on.

This chapter explains the SELECT DISTINCT statement.

SQL SELECT DISTINCT statement

In a table, you might include duplicate values. This is not a problem, but sometimes you may want to list only the different values (distinct).

Keyword DISTINCT is used to return only a different value.

syntax: SELECT DISTINCT column name from table name using DISTINCT keyword

If you want to select all the values from the company column, we need to use the SELECT statement:

SELECT Company from Orders "orders" table:

company OrderNumber IBM 3532 w3school 2356 Apple 4698 w3school 6953

Results:

company IBM W3school Apple W3school

Note that in the result set, W3school is listed two times.

To select only a different value from the company column, we need to use the Select DISTINCT statement:

SELECT DISTINCT Company from Orders results:

Company IBM W3school Apple

Now, in the result set, "W3school" is listed only once.