SQLzoo.net

Reference section

SELECT
[SQLite|DB2|Access|Postgres|Oracle|SQL Server|MySQL|Mimer|Sybase]
Building queries
CREATE, DROP and ALTER
[SQLite|DB2|Access|Postgres|Oracle|SQL Server|MySQL|Mimer|Sybase]
How to create tables, indexes, views and other things. How to get rid of them. How to change them.
INSERT, UPDATE and DELETE
[SQLite|DB2|Access|Postgres|Oracle|SQL Server|MySQL|Mimer|Sybase]
How to put records into a table, change them and how to take them out again.
DATES
[SQLite|DB2|Access|Postgres|Oracle|SQL Server|MySQL|Mimer|Sybase]
How to work with dates; adding, subtracting and formatting.
FUNCTIONS
[SQLite|DB2|Access|Postgres|Oracle|SQL Server|MySQL|Mimer|Sybase]
How to use string functions, logical functions and mathematical functions.
USERS
[SQLite|DB2|Access|Postgres|Oracle|SQL Server|MySQL|Mimer|Sybase]
How to create users, give them access, get at other peoples tables. How to find processes and kill them.
META DATA
[SQLite|DB2|Access|Postgres|Oracle|SQL Server|MySQL|Mimer|Sybase]
Information about the database: what tables exist, what are the column headings, what database is in use.
Error Messages
[SQLite|DB2|Access|Postgres|Oracle|SQL Server|MySQL|Mimer|Sybase]
Error messages, how they are caused and what can be done about them.