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Written by Andrew Gould
In this tutorial
All of the queries we've created in this tutorial so far have each used a single criterion. In this part of the series we're going to look at how to combine criteria using the AND and OR logical operators. We'll also cover how to use the NOT operator to exclude records from the results of a query.
When you want to create a list of criteria which must all be met you can use the AND keyword:
SELECT
FilmName
,FilmReleaseDate
,FilmRunTimeMinutes
FROM
tblFilm
WHERE
FilmName LIKE '%star%' AND
FilmReleaseDate > '1979-12-31' AND
FilmRunTimeMinutes > 120
In order for a film to be displayed in the results its name must contain the word star, its release date must be after 1979 and its running time must be greater than 120. The results of this query are shown below:
Each of these films match all three of the specified criteria.
You can also join multiple criteria using the OR keyword. When you do this each record in the results only has to match a single one of the criteria in your list:
SELECT
FilmName
,FilmReleaseDate
,FilmRunTimeMinutes
FROM
tblFilm
WHERE
FilmName LIKE '%star%' OR
FilmReleaseDate > '1979-12-31' OR
FilmRunTimeMinutes > 120
In this example a film will show up in the results if it has the word star in its name, or if it was released after 1979, or if its running time is longer than 120 minutes. This means that we get a lot more records in our results:
Each of these films matches at least one of the specified criteria.
You can use a combination of AND and OR keywords in the same query. When you do this however, you have to be careful about the way SQL Server groups your criteria together.
In the example below I'd like to see any films that are longer than 120 minutes and which have the words star or war in their name:
SELECT
FilmName
,FilmRunTimeMinutes
FROM
tblFilm
WHERE
FilmName LIKE '%star%' OR
FilmName LIKE '%war%' AND
FilmRunTimeMinutes > 120
This should mean that a film will only be returned if its run time is greater than 120 minutes. Unfortunately, I don't get quite the results I want:
Some of the films which contain the word star are shorter than 120 minutes.
What SQL Server is returning is any film whose name contains the word star, as well as films that are longer than 120 minutes and which have the word war in their name. In essence, the first criterion is treated independently while the second two are grouped together.
We can override this behaviour by using parentheses (or brackets):
SELECT
FilmName
,FilmRunTimeMinutes
FROM
tblFilm
WHERE
(FilmName LIKE '%star%' OR
FilmName LIKE '%war%') AND
FilmRunTimeMinutes > 120
Adding a set of parentheses around the first two criteria will group them together and affect the results of the query:
This time we only see films which are longer than 120 minutes.
You can use multiple sets of parentheses in the same query to ensure that your criteria are evaluated in the way you want. The example below groups all of the criteria from the query shown above and adds another pair of criteria:
SELECT
FilmName
,FilmRunTimeMinutes
FROM
tblFilm
WHERE
--long films with star or war in name
((FilmName LIKE '%star%' OR
FilmName LIKE '%war%') AND
FilmRunTimeMinutes > 120)
OR
--short films with die in name
(FilmName LIKE '%die%' AND
FilmRunTimeMinutes < 120)
The results of this cheery query are shown below:
Judicious use of comments helps to remind you what you're trying to do!
We've already talked about how to write criteria asking where a field is not equal to a specific value, for example:
SELECT
FilmName
,FilmRunTimeMinutes
FROM
tblFilm
WHERE
FilmName <> 'Die Hard'
But what if you wanted to exclude all films which contain the words Die Hard? Unfortunately, this technique will not work:
SELECT
FilmName
,FilmRunTimeMinutes
FROM
tblFilm
WHERE
FilmName <> '%Die Hard%'
Instead you must use the LIKE keyword in combination with the NOT operator:
SELECT
FilmName
,FilmRunTimeMinutes
FROM
tblFilm
WHERE
FilmName NOT LIKE '%Die Hard%'
You can also use NOT in combination with IN, as shown below:
SELECT
FilmName
,FilmRunTimeMinutes
FROM
tblFilm
WHERE
FilmRunTimeMinutes NOT IN (90,120,150,180)
This query would show all films except those whose run times are exactly 90, 120, 150 or 180 minutes.
In the next part of this tutorial we're going to explain how to find values that aren't there using NULL.
You can learn more about this topic on the following Wise Owl courses:
Kingsmoor House
Railway Street
GLOSSOP
SK13 2AA
Landmark Offices
99 Bishopsgate
LONDON
EC2M 3XD
Holiday Inn
25 Aytoun Street
MANCHESTER
M1 3AE
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