The Access database adds fields with SQL statements, modifies fields, deletes fields _access

Here's an example:
Creates a table Table1 with the DDL create TABLE, the primary key is an AutoNumber field, and the other is a text field with a length of 10.

Copy Code code as follows:

CREATE TABLE Table1 (Id COUNTER CONSTRAINT PrimaryKey PRIMARY KEY, MyText TEXT (10))

To build a table Table2 with two fields, the field ID is a long integer, and the field MyText is text

Copy Code code as follows:

CREATE TABLE Table2 (Id LONG, MyText TEXT)

Use the following statement to establish a one-to-many relationship between Table1 and Table2, cascade Update, Cascade Delete:

Copy Code code as follows:

ALTER TABLE Table2 ADD CONSTRAINT Relation1 FOREIGN KEY ([id]) REFERENCES Table1 ([id]) on UPDATE CASCADE on DELETE Cascad E

Delete a relationship with the following statement:

Copy Code code as follows:

ALTER TABLE Table2 DROP CONSTRAINT Relation1

Delete Table1 with the following statement:

Copy Code code as follows:

DROP TABLE Table1

Set a field as the primary key

Copy Code code as follows:

ALTER TABLE 1 ALTER COLUMN [ID] COUNTER CONSTRAINT myprimarykey PRIMARY KEY

Add a field mysalary

Copy Code code as follows:

ALTER TABLE AAA add COLUMN mysalary CURRENCY

Delete a field mysalary

Copy Code code as follows:

ALTER TABLE AAA drop COLUMN mysalary