Oracle 5.0, Справочное руководство

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USE
Syntax
1213
| Functions | Comparison operators | Y |
| Functions | Control flow functions | Y |
| Functions | Date and Time Functions | Y |
| Functions | Encryption Functions | Y |
| Functions | Information Functions | Y |
| Functions | Logical operators | Y |
| Functions | Miscellaneous Functions | Y |
| Functions | Numeric Functions | Y |
| Functions | String Functions | Y |
+----------------------+-------------------------+----------------+
If you intend to use the
HELP
statement while other tables are locked with
LOCK TABLES
, you must
also lock the required
mysql.help_xxx
tables.
13.8.4.
USE
Syntax
USE db_name
The
USE db_name
statement tells MySQL to use the
db_name
database as the default (current)
database for subsequent statements. The database remains the default until the end of the session or
another
USE
statement is issued:
USE db1;
SELECT COUNT(*) FROM mytable; # selects from db1.mytable
USE db2;
SELECT COUNT(*) FROM mytable; # selects from db2.mytable
Making a particular database the default by means of the
USE
statement does not preclude you from
accessing tables in other databases. The following example accesses the
author
table from the
db1
database and the
editor
table from the
db2
database:
USE db1;
SELECT author_name,editor_name FROM author,db2.editor
WHERE author.editor_id = db2.editor.editor_id;