SQL DROP DATABASE can be used to delete databases .
Example
mysql> DROP DATABASE database_name;
Query OK, 1 row affected (0.54 sec)
Tag Archives: PHP
SQL DROP TABLE
SQL DROP TABLE can be used to delete tables .
Example
mysql> DROP TABLE user2;
Query OK, 0 rows affected (0.01 sec)
SQL DROP INDEX
SQL DROP INDEX can be used to delete indexes
Example
mysql> ALTER TABLE users DROP INDEX user_index;
Query OK, 5 rows affected (0.10 sec)
Records: 5 Duplicates: 0 Warnings: 0
SQL DROP
SQL DROP can be used to delete table,indexes and databases
Below given are the SQL DROP dtatements
SQL DROP INDEX – Delete indexes
SQL DROP TABLE – Delete tables
SQL DROP DATABASE – Delete databases
SQL CREATE INDEX
SQL CREATE INDEX is used to create indexes in tables.
It let the database application to find data fast .
Example
mysql> CREATE INDEX user_index ON users (uid);
Query OK, 5 rows affected (0.12 sec)
Records: 5 Duplicates: 0 Warnings: 0
SQL DEFAULT
SQL DEFAULT is used to insert a default value into a column.
The default value will be added to all new records, if no other value is given.
Example
CREATE TABLE users(uid int NOT NULL,name varchar(255) NOT NULL DEFAULT ‘phpcode’)
SQL CHECK
SQL CHECK is used to limit the value range that can be placed in a column.
If you define a CHECK constraint on a single column it allows only certain values for this column.
If you define a CHECK constraint on a table it can limit the values in certain columns based on values in other columns in the row.
Example
CREATE TABLE users(uid int NOT NULL,name varchar(255) NOT NULL,CHECK (uid>0))
SQL FOREIGN KEY
SQL FOREIGN KEYin one table points to the primary key of another table .
Table – users
+—-+——+
| uid | name |
+—-+——+
| 1 | AAAA |
| 2 | BBBB |
| 3 | CCCC |
| 4 | DDDD |
| 5 | EEEE |
+—-+——+
Table – orders
+—–+—–+——–+
| oid | uid | items |
+—–+—–+——–+
| 1 | 1 | Pen |
| 2 | 2 | Watch |
| 3 | 3 | shoe |
| 4 | 4 | mobile |
+—–+—–+——–+
Here the field uid in the table orders points to the column uid in users .
That is uid in the orders is the foreign key and that in users is primary key
FOREIGN KEY constraint prevent any action that may destroy the relation between the tables.
It also prevent invalid data and make sure that the data to be inserted should be one of the primary key value in another
Example
CREATE TABLE IF NOT EXISTS `orders` (
`oid` int(11) NOT NULL AUTO_INCREMENT,
`uid` int(11) NOT NULL,
`items` varchar(255) NOT NULL,
PRIMARY KEY (`oid`),
FOREIGN KEY (uid) REFERENCES users(uid)
)
Cannot access admin panel after migration vbulletin
Upload tools.php from the do_not_upload folder into your admincp folder. Point your browser to it and reset the cookie domain. You cannot simply do that to one field in the database.
Before pointing the browser to the page , add the below given code in includes/config.php
.Add this line right under <?php
define(‘DISABLE_HOOKS’, true);
That would fix the issue
SQL PRIMARY KEY
SQL PRIMARY KEY uniquely identifies each record in a database table.
Primary keys must contain unique values and primary key column cannot contain NULL
values. A table can not have more than one primary key .
Example
mysql> CREATE TABLE `new_users` (`id` int(11) NOT NULL AUTO_INCREMENT, `name` varchar(255) NOT NULL, PRIMARY KEY (`id`));
Query OK, 0 rows affected (0.10 sec)
Pramod T P 