SQL Select Distinct and Select Where

 

SQL SELECT DISTINCT Statement

The SELECT DISTINCT statement is used to return only distinct (different) values.

Inside a table, a column often contains many duplicate values; and sometimes you only want to list the different (distinct) values.

SELECT DISTINCT Syntax

SELECT DISTINCT column1, column2, ...

FROM table_name;

SELECT Example Without DISTINCT

The following SQL statement selects all (including the duplicates) values from the "Country" column in the "Customers" table:

 SELECT Country FROM Customers; 

 

SELECT DISTINCT Examples

The following SQL statement selects only the DISTINCT values from the "Country" column in the "Customers" table:

SELECT DISTINCT Country FROM Customers;

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The SQL WHERE Clause

The WHERE clause is used to filter records.

It is used to extract only those records that fulfill a specified condition.

WHERE Syntax

SELECT column1, column2, ...

FROM table_name

WHERE condition;

The WHERE clause is not only used in SELECT statements, it is also used in UPDATE, DELETE, etc.! 

Demo Database

WHERE Clause Example

SQL statement selects all the customers from the country "Mexico", in the "Customers" table:

SELECT * FROM Customers WHERE Country='Mexico';

 Output:

Text Fields vs. Numeric Fields

SQL requires single quotes around text values (most database systems will also allow double quotes).

However, numeric fields should not be enclosed in quotes:

Operators in The WHERE Clause

 The following operators can be used in the WHERE clause: