SQL WHERE Clause
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
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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'
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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
!=
…
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