The WHERE clause is used to filter records. The WHERE Clause The WHERE clause is used to extract only those records that fulfill a specifi...
The WHERE clause is used to filter records.
The WHERE Clause
The WHERE clause is used to extract only those records that fulfill a specified criterion.SQL WHERE Syntax
SELECT column_name(s) FROM table_name WHERE column_name operator value |
WHERE Clause Example
The "Persons" table:| P_Id | LastName | FirstName | Address | City |
|---|---|---|---|---|
| 1 | Hansen | Ola | Timoteivn 10 | Sandnes |
| 2 | Svendson | Tove | Borgvn 23 | Sandnes |
| 3 | Pettersen | Kari | Storgt 20 | Stavanger |
Now we want to select only the persons living in the city "Sandnes" from the table above.
We use the following SELECT statement:
SELECT * FROM Persons WHERE City='Sandnes' |
The result-set will look like this:
| P_Id | LastName | FirstName | Address | City |
|---|---|---|---|---|
| 1 | Hansen | Ola | Timoteivn 10 | Sandnes |
| 2 | Svendson | Tove | Borgvn 23 | Sandnes |
Quotes Around Text Fields
SQL uses single quotes around text values (most database systems will also accept double quotes).Although, numeric values should not be enclosed in quotes.
For text values:
This is correct: SELECT * FROM Persons WHERE FirstName='Tove' This is wrong: SELECT * FROM Persons WHERE FirstName=Tove |
For numeric values:
This is correct: SELECT * FROM Persons WHERE Year=1965 This is wrong: SELECT * FROM Persons WHERE Year='1965' |
Operators Allowed in the WHERE Clause
With the WHERE clause, the following operators can be used:| Operator | Description |
| = | Equal |
| <> | Not equal |
| > | Greater than |
| < | Less than |
| >= | Greater than or equal |
| <= | Less than or equal |
| BETWEEN | Between an inclusive range |
| LIKE | Search for a pattern |
| IN | If you know the exact value you want to return for at least one of the columns |
Note: In some versions of SQL the <> operator may be written as !=
