Using SQL Standards? Database SQL comparition

transcript

SQL COMPARISONDenish Patel

Database AdministratorOmniTi Computer Consulting Inc

Using SQL Standards

Friday, April 2, 2010

SQL STANDARDS

SQL 2003

SQL 2008

DATABASES

Oracle 10g Express Edition

PostgreSQL 8.3.3

MySQL 5.0.18

SQL92:Updatable views can not be derived from more than one base table

SQL99: As long as it “make sense”

SQL:2008: As long as the update-operation translates into unambiguous change

Oracle Conforms at least SQL92

PostgreSQLBreak rules by not allowing

updatable views but offer non-standard ‘rule’ system

MySQL Conforms at least SQL92

JOIN TYPES

Oracle PostgreSQL MySQL

Natural Join Yes Yes Yes

Using-clause Yes Yes Yes

Full Join Yes Yes No

Explicit(Cross Join)

Yes Yes Yes

ORDER BY

SQL Standard : Relations are unordered but result sets may be ordered when returned to the user using cursor

Doesn’t specify NULLs order

NULLs are equally ordered and can be first or last

...ORDER BY...NULLS FIRST

...ORDER BY ...NULLS LAST

DECLARE cursorname CURSOR FOR

SELECT ...FROM ....WHERE...

ORDER BY column_name1,column_name2,....

ORDER BY

Oracle- Cursor allows ORDER BY

- By Default NULLs considered higher- ORDER BY ... NULLS LAST

PostgreSQL- Cursor allows ORDER BY

- By Default NULLs considered higher- ORDER BY ... NULLS LAST

Cursor allows ORDER BY- By Default NULLs considered lower

- minus(-) character used to change from ASC to DESC or Vice-Versa

SIMPLE LIMIT

FETCH FIRST (Since SQL:2008)

Window Function(Since SQL:2003)

Cursor

SELECT ...FROM ..WHERE...ORDER BY...FETCH FIRST n ROW(s) ONLY

SELECT * FROM

( SELECT ROW_NUMBER() OVER (ORDER BY key ASC) as rownumber, columns

FROM tablename ) as foo

WHERE rownumber <=n

DECLARE , OPEN , FETCH , CLOSE

SIMPLE LIMIT

Oracle-Supports ROW_NUMBER but not FEATCH

PostgreSQL

- Doesn’t support ROW_NUMBER() or FETCH FIRST

- Alternative LIMIT(*SELECT ..FOR UPDATE)

- Doesn’t support ROW_NUMBER() or FETCH FIRST

- Alternative LIMIT

MULTI- INSERT

OracleNot Supported

insert into tablename values (0,‘foo’);insert into tablename values (1,‘bar’);

PostgreSQLSupported

insert into tablename values (0,‘foo’), (1,‘bar’);

MySQLSupported

insert into tablename values (0,‘foo’), (1,‘bar’);

TYPES- BOOLEAN

BOOLEAN type is Optional!!

TRUE, FALSE, UNKNOWN or NULL

UNKNOWN can be NULL!

TRUE > FALSE

TYPES- BOOLEAN

OracleNot Supported

Alternative NUMBER(1)Do not forget to add constraint

PostgreSQLFollow Standards

Does not accept UNKNOWN

MySQLNonconforming alternative TINYINT(1)

Accept values greater than 1

TYPES- CHAR

CHAR-length

Return error if the inserted sting is too long except spaces

Pad with spaces if string is shorter

Casting or Compare (VARCHAR) - Pad with trailing spaces

TYPES- CHAR

OracleGenerally Follows Standard

Doesn’t remove trailing spaces when exceeds CHAR length

PostgreSQLGenerally Follows Standard

Truncate trailing spaces i.e CHARACTER_LENGTH

MySQLBreaks the rules

Silently inserting truncated stringTruncates all trailing spaces

TYPES- TIMESTAMP

second - 6 fractional digits

TIMESTAMP ‘2009-03-05 16:10:18.299411’

TIMESTAMP WITH TIME ZONE

TIMESTAMP ‘2009-03-05 16:10:18.299411+05:00’

TYPES- TIMESTAMP

Oracle Follows standard

PostgreSQLFollows Standards with exceptionTIMESTAMP & TIMESTAMPTZIllogical Standard is Standard!

Not SupportedMagical TIMESTAMP datatype

No Sanity checks on the date ‘2009-03-32 00:00:00’

UNIQUE CONSTRAINT

Unique Values or NULL

NULL <> NULL

Nulls allowed feature

create table test(a number,b number, unique (a,b));

insert into test values (1,NULL);

insert into test values(1,NULL);

UNIQUE CONSTRAINT

Oracle Follows standard without Nulls allowed

PostgreSQL Follows standard with Nulls Allowed

MySQL Follows standard with Nulls Allowed

AUTO KEY

GENERATED .. [ALWAYS /BY DEFAULT] AS IDENTITY

ALWAYS - user can not specify value

BY DEFAULT - user can manually specify value

AUTO KEY

OracleDoes not support IDENTIFY attribute

Sequence & TriggerException to implement ALWAYS

PostgreSQLDoes not support IDENTIFY attribute

In-line SERIAL attribute Trigger to implement ALWAYS

Does not support IDENTIFY attributeAUTO INCREMENT

Never fails (!)

TRUNCATE TABLE

Delete all rows without causing triggered action

Need more clarification on

TRUNCATE TABLE should be allowed in transaction

Immediate Commit

TRUNCATE TABLE

OracleFollows the standard

Implicit commit

PostgreSQLFollows the standard

Allowed with other transaction Does not implicit commit

Doesn’t ALWAYS follow standardSlow and Trigger Invoking

For Innodb, Allowed with other transaction & does implicit commit

CL- interfaceDefault port

DB NameVersion Name

List Schema List Tables

Oracle sqlplus1521

select name from v$database;select * from v$version;

select username from all_users;select * from tab;

PostgreSQL psql5432

\l or psql --listselect version();

\dn or select schemaname from information_schema.schemata;

\dt or select tablename from pg_tables;

MySQL mysql3306

show databases;select version();

Does not support schemashow tables;

RESOURCES

SQL Standards Documentations/Books:

SQL99: http://www.elsevierdirect.com/product.jsp?isbn=9781558606777

SQL2008: http://www.wiscorp.com/sql200n.zip (File 5CD2-02-Foundation-2006-01.pdf)

http://troels.arvin.dk/db/rdbms/#cli

Oracle Documentation: http://download.oracle.com/docs/cd/B19306_01/server.102/b14200/toc.htm

PostgreSQL Documentation: http://www.postgresql.org/docs/8.3/static/sql-commands.html

MySQL documentaion: http://dev.mysql.com/doc/refman/5.0/en/

THANK YOU!!

Using SQL Standards? Database SQL comparition

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