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To look up data, we write a query beginning with SELECT.
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The smallest SELECT statement must have a FROM clause as well, designating
the table name.
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SELECT * indicates that you want to select all columns.
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So, we could have the simple statement:
SELECT * FROM STUDENTS
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But, some tables have multiple columns, so if you want to state only specific
columns to be returned, enter the column names, comma separated, in place
of the *:
SELECT name, bearcatID FROM STUDENTS
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If you only want to select certain records, add a WHERE clause.
SELECT name, bearcatID FROM STUDENTS WHERE HomeCollegeID = 32
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Now, suppose you want to select records by joining students and
colleges. You'll need to specify both tables in the WHERE
clause and tell the database how to join them together in the FROM
clause.
SELECT name, bearcatID FROM STUDENTS, COLLEGES WHERE STUDENTS.HomeCollegeID
= COLLEGES.CollegeID
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But this returns all records for all students and colleges in our database,
assuming that each student has a college ID represented in the colleges
table. So what if we want to only select students from college 32?
We use an AND statement.
SELECT name, bearcatID FROM STUDENTS, COLLEGES WHERE STUDENTS.HomeCollegeID
= COLLEGES.CollegeID AND COLLEGES.CollegeID = 32
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We could have easily stated STUDENTS.HomeCollegeID = 32. Either way
works.
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32 is not surrounded by quotes because it is a number. If it were
a string, we'd surround it with quotes.
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SQL is case-insensitive, but the keywords (SELECT, FROM, WHERE)
are traditionally entered in upper case.
Action Queries
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