SQL REFERENCE - Concepts of Database Management - page 347

B

APPENDIX

SQL REFERENCE

You can use this appendix to obtain details concerning important components and syntax for SQL. Items are
arranged alphabetically. Each item contains a description and, where appropriate, both an example and a
description of the query results. Some SQL commands also include a description of the clauses associated with
them. For each clause, there is a brief description and an indication of whether the clause is required or optional.

ALTER TABLE

Use the ALTER TABLE command to change a table s structure. As shown in Figure B-1, you type the ALTER

TABLE command, followed by the table name, and then the alteration to perform. (Note: In Access, you usu-
ally make these changes to a table in Design view rather than using ALTER TABLE.)

'

Clause Description Required?

ALTER TABLE table name Indicates the name of the table to be altered. Yes

alteration Indicates the type of alteration to be performed. Yes

FIGURE B-1 ALTER TABLE command

The following command alters the Customer table by adding a new column named CustType:

ALTER TABLE Customer
ADD CustType CHAR(1)
;

The following command alters the Customer table by changing the length of the CustomerName column:

ALTER TABLE Customer
CHANGE COLUMN CustomerName TO CHAR(50)
;

The following command alters the Part table by deleting the Warehouse column:

ALTER TABLE Part
DELETE Warehouse
;

COLUMN OR EXPRESSION LIST (SELECT CLAUSE)

To select columns, use a SELECT clause with the list of columns separated by commas. The following
SELECT clause selects the CustomerNum, CustomerName, and Balance columns:

SELECT CustomerNum, CustomerName, Balance

Use an asterisk in a SELECT clause to select all columns in the table. The following SELECT command
selects all columns in the Part table:

SELECT *
FROM Part
;