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## Example files for the title:  

# SQL Hacks, by Andrew Cumming

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SQL Hacks Source code

Associated with SQL Hacks, Andrew Cumming and Gordon Russell, Pub O'Reilly

Buy the book! http://www.oreilly.com/catalog/sqlhks/reviews.html

Most hacks have three sections:

setup - These SQL commands create the tables or views required to run the hack

hack -  This is the code that generates the main hack. Sometimes there

        are several commands associated with a hack.

tidy -  This code removes the tables created by setup or sql.

--SQL Hacks, Hack 03: Conditional INSERT Statement

--mysql version

--------------

--   setup  --

--------------

CREATE TABLE libraryLoan

(member CHAR(5)

,book CHAR(5)

,dueDate DATE 

);

INSERT INTO libraryLoan VALUES ('jim01','bk002',DATE '2005-03-22');

INSERT INTO libraryLoan VALUES ('jim01','bk002',DATE '2005-09-21');

INSERT INTO libraryLoan VALUES ('ann02','bk005',DATE '2005-09-21');

INSERT INTO libraryLoan(member,book,dueDate)

  VALUES ('jim01','bk002',

          CURRENT_DATE + INTERVAL '14' DAY 

         );

INSERT INTO libraryLoan(member,book,dueDate)

  VALUES ('ann02','bk005',

          CURRENT_DATE - INTERVAL '1' DAY 

         );

CREATE TABLE libraryReturn

(book  CHAR(5)

,member CHAR(5)

,returnDate DATE

,fine       DECIMAL(10,2)

);

CREATE TABLE roomBooking

(who   VARCHAR(20)

,wht   VARCHAR(20) NOT NULL

,whn   DATE

            NOT NULL

,PRIMARY KEY (whn,wht)

);

--------------------

--       hack     --

--------------------

INSERT INTO libraryReturn(book,member,returnDate,fine)

  VALUES ('jim01','bk002',CURRENT_DATE,

          (SELECT 0.20

             FROM libraryLoan

           WHERE member='jim01' AND book='bk002'

           HAVING MAX(dueDate)<CURRENT_DATE));

INSERT INTO libraryReturn(book,member,returnDate,fine)

  VALUES ('ann02','bk005',CURRENT_DATE,

          (SELECT 0.20

             FROM libraryLoan

           WHERE member='ann02' AND book='bk005'

           HAVING MAX(dueDate)<CURRENT_DATE));

SELECT * FROM libraryReturn;

INSERT INTO roomBooking VALUES ('Col. Mustard','Ballroom',DATE '2006-07-13');

INSERT INTO roomBooking(whn,wht,who)

  SELECT DATE '2006-07-13','Billiard Room','Prof. Plum'

    FROM dual

    WHERE NOT EXISTS (SELECT who FROM roomBooking

                       WHERE whn = DATE '2006-07-13'

                         AND wht='Billiard room');

INSERT INTO roomBooking(whn,wht,who)

  SELECT DATE '2006-07-13','Ballroom','Miss. Scarlet'

    FROM dual

    WHERE NOT EXISTS (SELECT who FROM roomBooking

                       WHERE whn = DATE '2006-07-13'

                         AND wht='Ballroom');

SELECT * FROM roomBooking;

----------------

--    tidy    --

----------------

DROP TABLE libraryLoan;

DROP TABLE libraryReturn;

DROP TABLE roomBooking;