Programming techniques - OCRThe use of SQL to search for data

Databases use their own type of programming language. This language is known as structured query language, or SQL.

Example

Consider this simple personnel table with four records:

Retrieving data

Data can be retrieved using the commandsSELECT, FROM and WHERE

SELECT * FROM "personnel" WHERE "Title" = "Mr"

Note - * stands for wildcard, which means all records. This would retrieve the following data:

1001 Mr Alan Turing [email protected]

1004 Mr George Boole [email protected]

The LIKE command can be used to find matches for an incomplete word, for example:

SELECT * FROM "personnel" WHERE "email address" LIKE "%com"

This would retrieve:

1001 Mr Alan Turing [email protected]

1002 Mrs Ada Lovelace [email protected]

1004 Mr George Boole [email protected]

Note - %com is also a wildcard which will return any value that contains “com”.

Boolean operators AND and OR can also be used to retrieve data.

SELECT * FROM "personnel" WHERE "Surname" = "Turing" OR "Hopper"

This would retrieve:

1001 Mr Alan Turing [email protected]

1003 Miss Grace Hopper [email protected]