Structured Query Language is the language in which to talk to databases to make them retrieve or update data. It is contained in most relational database system programs, as Access, Oracle, Visual FoxPro, There are several dialects.
SQL commands are written in rows, with key words capitalized, and end with a semicolon.
This allows you to extract, change, update, and delete data in tables of a database.
|displays a whole table.|
|outputs the corresponding columns of the table.|
|outputs the corresponding columns of the table obeying the condition.|
The first variant displays certain columns. The second one only certain columns and certain rows. The WHERE-condition could be something like
Try the syntax on this interactive page.
VALUES (value1, value3);
|creates a new record with the corresponding values in the columns mentioned. Remember again to enclose all strings into single quotation marks.|
SET (column1=value1, column3=value3)
|condition could be something like first = 'Erich" and last = 'Prisner'|
|DELETE from tablename
|deletes all records obeying the condition|
You can also create tables with SQL, like
CREATE table tablename
(column1 varchar(10), column2 varchar(20), age number(3));
or delete them by DROP table tablename;
You can create, change, and delete tables, or define or delete keys.
Erich Prisner, 11/22/2003