Alter table: drop primary and foreign key : Alter Table « Table Index « SQL / MySQL






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Alter table: drop primary and foreign key

   
/*
mysql> Drop table Books;
Query OK, 0 rows affected (0.03 sec)

mysql> CREATE TABLE Books
    -> (
    ->    ID SMALLINT NOT NULL,
    ->    Name VARCHAR(40) NOT NULL,
    ->    PubID SMALLINT NOT NULL DEFAULT 'Unknown'
    -> )
    -> ENGINE=INNODB;
Query OK, 0 rows affected (0.17 sec)

mysql> Describe Books;
+-------+-------------+------+-----+---------+-------+
| Field | Type        | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| ID    | smallint(6) |      |     | 0       |       |
| Name  | varchar(40) |      |     |         |       |
| PubID | smallint(6) |      |     | 0       |       |
+-------+-------------+------+-----+---------+-------+
3 rows in set (0.00 sec)

mysql> ALTER TABLE Books
    -> DROP PRIMARY KEY,
    -> DROP FOREIGN KEY fk_1,
    -> DROP COLUMN Format;
ERROR 1091 (42000): Can't DROP 'PRIMARY'; check that column/key exists
mysql> Describe Books;
+-------+-------------+------+-----+---------+-------+
| Field | Type        | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| ID    | smallint(6) |      |     | 0       |       |
| Name  | varchar(40) |      |     |         |       |
| PubID | smallint(6) |      |     | 0       |       |
+-------+-------------+------+-----+---------+-------+
3 rows in set (0.00 sec)


*/

Drop table Books;

CREATE TABLE Books
(
   ID SMALLINT NOT NULL,
   Name VARCHAR(40) NOT NULL,
   PubID SMALLINT NOT NULL DEFAULT 'Unknown'
)
ENGINE=INNODB;

Describe Books;

  
ALTER TABLE Books
DROP PRIMARY KEY,
DROP FOREIGN KEY fk_1,
DROP COLUMN Format;

Describe Books;








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28.Storing Altered Character Strings
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31.Use the asterisk to try matching against the name ian or the alternative spelling, iain.
32.Specifying Multiple Alterations
33.Alter table to add an index
34.Alter table to add unique index
35.Alter table to Delete an Index
36.Alter table to add index
37.To drop an index with ALTER TABLE
38.Reduce the number of significant characters per index in the index to the first 16 characters
39.Add IGNORE to the statement, then use SELECT to have a look at the table contents to see how the duplicates ha
40.Change j from INT to BIGINT
41.MODIFY statement should specify the null and default value attributes explicitly
42.Redefine i to be NOT NULL, then try again
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