MySQL First knowledge 3

With the familiarity of MySQL, this time to summarize the MySQL database delete, backup and restore operations

1. Deletion of the database:

A. Command to delete a database: Drop DB dbname;

B. Deleting a table from a database:

Single table: Drop TABLE tablename;

Multiple tables: Drop table tablename1,tablename2,tablename2; (Note that there are no fewer commas here, but when backing up multiple tables, there is no comma between multiple tables, which is written below)

C. Deleting records from a table: Delete;truncate table Two methods

Delete command: Delete from tablename (WHERE ..... LIMIT ....)

Can delete all records, or according to the criteria to choose to delete some of the data, the use of more flexible;

TRUNCATE command: TRUNCATE TABLE tablename;

Delete all records, cannot attach conditional clauses;

There is also a small difference: Delete can return the number of records deleted, TRUNCATE returns the number of records is 0 (the specific application of the two differences is not familiar with, and then after the familiar and then fill in)

2. Backup & Restore

Single database backup command: Mysqldump-u root-p dbname >/home/wuliang/dbname_backup.sql (dbname is the name of the database that needs to be backed up,/home/wuliang these are required for backup files Saved paths,. SQL backup files are stored in this format)

Table Backup in database: Mysqldump-u root-p dbname table1 table2 table3 >/home/wuliang/name_backup.sql (Note: There is no need to separate commas between multiple tables)

Multiple database backup commands: Mysqldump-u root-p--databases dbname1 dbname2 dbname3 >/home/wuliang/bcakup.sql (--databases to declare multiple databases)

Full database backup: Mysqldump-u root-p-all-databases >/home/wuliang/backup.sql (-all-databases to declare all databases)

Database restore: Mysql-u root-p

Welcome to files in database: Mysql-u root-p dbname

MySQL First knowledge 3