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Getting to Know SQL
© Jim Hope 2002 All Rights Reserved
Data Manipulation SELECT statement INSERT INTO statement UPDATE statement DELETE statement TRANSFORM statement UNION operation
© Jim Hope 2002 All Rights Reserved
Data Definition CREATE TABLE statement CREATE INDEX statement ALTER TABLE statement CONSTRAINT clause DROP statement SELECT... INTO statement
© Jim Hope 2002 All Rights Reserved
Example 1SELECT *
FROM people ;
Means: Select all the fields (*) for all rows from the table called people
© Jim Hope 2002 All Rights Reserved
Example 2Specify FieldsSELECT lastname, firstname
FROM people ;
Means: Select the fields (lastname and firstname) for all rows from the table called people
© Jim Hope 2002 All Rights Reserved
Example 3aSetting the ScopeSELECT lastname, firstname, score
FROM people
WHERE score >=250
Means: Select the fields (lastname, firstname, score) for only rows where the score is greater than or equal to 250
© Jim Hope 2002 All Rights Reserved
Example 3bSetting the ScopeSELECT lastname, firstname, score
FROM people
WHERE score >=250 OR score <=100
Means: Select the fields (lastname and firstname, score) for only rows where the score is greater than or equal to 250 or the score is less than or equal to 100
© Jim Hope 2002 All Rights Reserved
Example 4aSetting the OrderSELECT lastname, firstname
FROM people
ORDER BY lastname ;
Means: Select the fields (lastname and firstname) for all rows from the table called people, in alphabetical (ascending) order by the values in the lastname field.
© Jim Hope 2002 All Rights Reserved
Example 4bSetting the OrderSELECT lastname, firstnameFROM peopleORDER BY lastname, firstname ;
Means: Select the fields (lastname and firstname) for all rows from the table called people, in alphabetical (ascending) order by the values in the lastname field. If there are duplicates – use the firstname (ascending)
© Jim Hope 2002 All Rights Reserved
Example 4cSetting the OrderSELECT lastname, firstname, scoreFROM peopleORDER BY score DESC, lastname,
firstname;Means: Select the fields (lastname and
firstname) for all rows from the table called people, in (descending) order by the values in the score field.
© Jim Hope 2002 All Rights Reserved
Example 4dSetting the Order – you trySELECT lastname, firstname, score
FROM people
ORDER BY score DESC
What would you do if you wanted to see duplicate scores presented alphabetically
© Jim Hope 2002 All Rights Reserved
Example 5aPutting things togetherSELECT lastname, firstname, score,
FROM people
WHERE score >=290 or score <=100
ORDER BY score DESC
What is this doing, and what else would you add?
© Jim Hope 2002 All Rights Reserved
Example 5bPutting more things togetherSELECT lastname, firstname, score,city
FROM people
WHERE (score >=290 or score <=100) and city <> "Surrey"
ORDER BY score DESC
What is this doing, and what else would you add?
© Jim Hope 2002 All Rights Reserved
Example 5cMore Scoping with INSELECT lastname, firstname, scoreFROM peopleWHERE lastname IN ("Bundy", "Simpson", "Petrie");(much better than… WHERE lastname = “Bundy” OR
lastname = “Simpson” ORlastname = “Petrie”
© Jim Hope 2002 All Rights Reserved
Example 5dWhatnotSELECT lastname, firstname, score
FROM people
WHERE lastname
NOT IN ("Bundy", "Simpson", "Petrie");
Try this one
© Jim Hope 2002 All Rights Reserved
Example 6aCountingSELECT count(*)
FROM people
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Example 6bCountingSELECT count(*)
FROM people
WHERE score <100
© Jim Hope 2002 All Rights Reserved
Example 7WildcardsSELECT lastname, firstname
FROM people
WHERE lastname like 'b*‘
(WHERE lastname like 'b%‘)
© Jim Hope 2002 All Rights Reserved
Example 8You can do math?SELECT lastname, firstname, score,
score +10 as bigscore
FROM people
ORDER BY score DESC
© Jim Hope 2002 All Rights Reserved
Example 9Create an AliasSELECT lastname +", " + firstname
as fullname
FROM people
ORDER BY lastname, firstname
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Example 10aMax & MinSELECT max (score)
FROM people
SELECT min (score)
FROM people
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Example 10bMax againSELECT lastname, firstname, score
FROM people
WHERE score = (SELECT max(score) FROM people);
This is a subquery
© Jim Hope 2002 All Rights Reserved
Example 11Keeping things DISTINCTSELECT DISTINCT city
FROM people;
© Jim Hope 2002 All Rights Reserved
Example 12aMore than one tableSELECT lastname, firstname, score,
[show name]
FROM people, show ;
This creates a Cartesian Product
© Jim Hope 2002 All Rights Reserved
Example 12bMore than one tableSELECT lastname, firstname, score,
[show name]
FROM people, show
WHERE people.show=show.show ;
© Jim Hope 2002 All Rights Reserved
Example 12cUsing JoinSELECT lastname, firstname, score,
[show name]
FROM People INNER JOIN Show ON people.show = show.show ;
FROM people, show
WHERE people.show=show.show ;
© Jim Hope 2002 All Rights Reserved
Example 12cUsing JoinSELECT lastname,
firstname, score, [show name]
FROM People INNER JOIN Show ON people.show = show.show ;
© Jim Hope 2002 All Rights Reserved
Example 12dUsing Left JoinSELECT lastname,
firstname, score, [show name]
FROM People Left JOIN Show ON people.show = show.show ;
© Jim Hope 2002 All Rights Reserved
Example 12eUsing Right JoinSELECT lastname,
firstname, score, [show name]
FROM People Right JOIN Show ON people.show = show.show ;
© Jim Hope 2002 All Rights Reserved
That’s enough of that
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