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SQL - Structure Query Language
- used to manipulate most databases existing today
- highly standard, but few differences depending on manufacturer
Operations:
select - allows you to select a set of fields from one or more tables according to a specific criteria. Refer to the sample tables for the examples.
Example 1: Select fields from one table:
select <list of fields> from <table>
select name,college from students
select name,department from instructor
Example 2: Now, you can filter to narrow your results:
select <list of fields> from <table> where <condition>
select name,collge from students where college='Merrill'
Example 3: You can also join one table to another and select from the result:
select <list of fields> from <table> left join <other table> on <matching condition>
select name,coursecode from students left join enrollment on students.studentid=enrollment.studentid
Notice that you may have to use the table name to qualify fields that have the same name.
Example 4: You can also sort the results by one or more fields:
order by <list of fields>
select name,coursecode from students left join enrollment on students.studentid=enrollment.studentid order by coursecode,name
Example 5: You can also have a field that "count" the records
count(*)
select count(*) from classes
select coursecode,count(*) from classes group by coursecode