Using Relational Databases and SQL Steven Emory Department of Computer Science California State University, Los Angeles Lecture 9: Data Manipulation Language

Miscellany School is almost over Last 3 lectures are pretty relaxing DML (How to update and modify a database) DDL (How to create a database)‏ Database Design (How to design a database)‏

Topics for Today Inserting Records (Pages 164 – 167)‏ Deleting Records (Pages 167 – 168)‏ Updating Records (Pages 168 – 173)‏ Transactions (Pages 173 – 179)‏

Before We Start When inserting and deleting data, you are going to mess up because nobody is perfect If you mess up there are two ways to restore the original database: Remove and restore the tables Use transactions (use BEGIN and ROLLBACK)‏ I prefer using BEGIN and ROLLBACK

Inserting Records Two syntaxes: INSERT INTO Insert one record at a time INSERT SELECT Insert one or more records at a time

Inserting Records INSERT INTO Syntax -- Form #1: Insert whole record. INSERT INTO tablename VALUES(value1, value2,..., valuen); -- Form #2: Insert partial record. INSERT INTO tablename(field1, field2,..., fieldn) VALUES(value1, value2,..., valuen);

Inserting Records INSERT SELECT Syntax -- Form #1: Insert whole record. INSERT INTO destination_table SELECT field1, field2,..., fieldn FROM source_tables WHERE conditions; -- Form #2: Insert partial record. INSERT INTO destination_table(df1, df2,..., dfn) SELECT sf1, sf2,..., sfn FROM source_tables WHERE conditions;

INSERT Examples Examples: Josh Scott Wagner was just hired by Lyric Music as a salesperson working under supervisor Bob Bentley. Base salaries for new recruits are set at $ Add Josh to the database. INSERT INTO SalesPeople VALUES(5, 'Josh', 'Wagner', 'jsw', 50.00, 1); Note that we have to use 1 instead of using a subquery. MySQL doesn't allow INSERT INTO and a subquery selection from the same table. SELECT SalesID FROM SalesPeople WHERE FirstName = 'Bob' AND LastName = 'Bentley';

INSERT Examples Way around it is to use INSERT SELECT INSERT INTO + subquery from same table = NO! INSERT INTO SalesPeople VALUES(5, 'Josh', 'Wagner', 'jsw', 50.00, (SELECT SalesID FROM SalesPeople WHERE FirstName = 'Bob' AND LastName = 'Bentley')); INSERT SELECT from same table = OK! INSERT INTO SalesPeople SELECT 5, 'Josh', 'Wagner', 'jsw', 50.00, SalesID FROM SalesPeople WHERE FirstName = 'Bob' AND LastName = 'Bentley';

INSERT Examples Example: Bobby Crum, a member of 21 West Elm, has also decided to join The Neurotics. Update the table XrefArtistsMembers to reflect this. Bobby won't be the responsible member for the artist he his joining. INSERT INTO XrefArtistsMembers VALUES((SELECT ArtistID FROM Artists WHERE ArtistName = 'The Neurotics'), (SELECT MemberID FROM Members WHERE FirstName = 'Bobby' AND LastName = 'Crum'), 0);

INSERT Examples Example: -- All members of 21 West Elm have decided to also become members of The Neurotics (as non- responsible members). Update the table XrefArtistsMembers to reflect this. INSERT INTO XrefArtistsMembers SELECT MemberID, (SELECT ArtistID FROM Artists WHERE ArtistName = 'The Neurotics'), 0 FROM Members JOIN XrefArtistsMembers USING(MemberID) JOIN Artists USING(ArtistID) WHERE ArtistName = '21 West Elm';

Deleting Records Deletes one or more rows from a table Deletes all rows without WHERE condition Single-Table DELETE Syntax DELETE FROM tablename WHERE conditions; Multi-Table DELETE Syntax Not in book Complicated and ugly! On next slide

Deleting Records Multi-table DELETE Syntax #1 (Preferred)‏ DELETE T1, T2,..., Tn FROM T1 JOIN T2 JOIN... JOIN Tn WHERE conditions; Note: If you use table alias in the FROM clause, you must use the alias in the DELETE clause as well (see examples later on). Multi-table DELETE Syntax #2 (Ugly)‏ DELETE FROM T1, T2,..., Tn USING T1 JOIN T2 JOIN... JOIN Tn WHERE conditions;

DELETE Examples Examples: -- Delete all rows from the Artists table. DELETE FROM Artists; -- Delete all titles by The Neurotics (subquery). DELETE FROM Titles WHERE ArtistID = (SELECT ArtistID FROM Artists WHERE ArtistName = 'The Neurotics'); -- Delete all titles by The Neurotics (multi-table). DELETE T FROM Titles T JOIN Artists A WHERE A.ArtistID = T.ArtistID AND A.ArtistName = 'The Neurotics';

DELETE Examples Examples: -- Delete all titles and tracks by the The Neurotics. DELETE T, K FROM Artists A JOIN Titles T JOIN Tracks K WHERE A.ArtistID = T.ArtistID AND T.TitleID = K.TitleID AND A.ArtistName = 'The Neurotics'; -- Delete The Neurotics from the Artists table and all titles and tracks by the them as well. DELETE A, T, K FROM Artists A JOIN Titles T JOIN Tracks K WHERE A.ArtistID = T.ArtistID AND T.TitleID = K.TitleID AND A.ArtistName = 'The Neurotics';

Updating Records To update existing records: -- Single-table syntax. UPDATE tablename SET field1 = value1, field2 = value2,... WHERE conditions; -- Multi-table equi-join syntax. UPDATE tablename1, tablename2,... SET field1 = value1, field2 = value2,... WHERE conditions; -- Multi-table subquery syntax. UPDATE tablename SET field1 = subquery1, field2 = subquery2,... WHERE conditions;

Updating Examples Example: -- The Bullets have decided to change their name to The Rockets. Update the database to reflect this change. UPDATE Artists SET ArtistName = 'The Rockets' WHERE ArtistName = 'The Bullets';

Updating Examples Example: -- The Bullets have decided to change their name to The Rockets and update their web domain to Update the database to reflect these changes. UPDATE Artists SET ArtistName = 'The Rockets', WebAddress = ' WHERE ArtistName = 'The Bullets';

Updating Examples Example: -- All members that had Bob Bentley as a sales contact will now have Scott Bull as a sales contact. Update the database to reflect these changes. Use the subquery syntax. UPDATE Members SET SalesID = (SELECT SalesID FROM SalesPeople WHERE FirstName = 'Scott' AND LastName = 'Bull') WHERE SalesID = (SELECT SalesID FROM SalesPeople WHERE FirstName = 'Bob' AND LastName = 'Bentley');

Updating Examples Example: -- All members that had Bob Bentley as a sales contact will now have Scott Bull as a sales contact. Update the database to reflect these changes. Use the join syntax. UPDATE Members M, SalesPeople S SET M.SalesID = (SELECT SalesID FROM SalesPeople WHERE FirstName = 'Scott' AND LastName = 'Bull') WHERE M.SalesID = S.SalesID AND S.FirstName = 'Bob' AND S.LastName = 'Bentley';

Transactions ACID Atomicity Consistency Isolation Durability SQL Keywords BEGIN/START TRANSACTION COMMIT ROLLBACK