Using Relational Databases and SQL

Steven EmoryDepartment 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 tablenameVALUES(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_tableSELECT field1, field2, ..., fieldnFROM source_tablesWHERE conditions;

-- Form #2: Insert partial record.INSERT INTO destination_table(df1, df2, ..., dfn)SELECT sf1, sf2, ..., sfnFROM source_tablesWHERE 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 $50.00. Add Josh to the database.INSERT INTO SalesPeopleVALUES(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 WHEREFirstName = 'Bob' AND LastName = 'Bentley';

INSERT Examples

Way around it is to use INSERT SELECT

INSERT INTO + subquery from same table = NO!INSERT INTO SalesPeopleVALUES(5, 'Josh', 'Wagner', 'jsw', 50.00,(SELECT SalesID FROM SalesPeople WHEREFirstName = 'Bob' AND LastName = 'Bentley'));

INSERT SELECT from same table = OK!INSERT INTO SalesPeopleSELECT 5, 'Josh', 'Wagner', 'jsw', 50.00, SalesIDFROM 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 XrefArtistsMembersVALUES((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 XrefArtistsMembersSELECT MemberID, (SELECT ArtistID FROM Artists WHERE ArtistName = 'The Neurotics'), 0FROM 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

DELETEFROM tablenameWHERE 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, ..., TnFROM T1 JOIN T2 JOIN ... JOIN TnWHERE 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)

DELETEFROM T1, T2, ..., TnUSING T1 JOIN T2 JOIN ... JOIN TnWHERE conditions;

DELETE Examples

Examples:

-- Delete all rows from the Artists table.DELETE FROM Artists;

-- Delete all titles by The Neurotics (subquery).DELETE FROM TitlesWHERE ArtistID = (SELECT ArtistID FROMArtists WHERE ArtistName = 'The Neurotics');

-- Delete all titles by The Neurotics (multi-table).DELETE T FROM Titles TJOIN Artists AWHERE A.ArtistID = T.ArtistID ANDA.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 RecordsTo update existing records:

-- Single-table syntax.UPDATE tablenameSET 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 tablenameSET 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 ArtistsSET 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 www.therockets.com. Update the database to reflect these changes.UPDATE ArtistsSET ArtistName = 'The Rockets', WebAddress = 'www.therockets.com'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 MembersSET 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 SSET 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