Database¶
Create Database¶
CREATE DATABASE [IF NOT EXISTS] {db_name | '[path/]db_name'} [db_option] ...
db_option:
ENGINE = {MMAP | MEMORY}
| LOCKMODE = {THREAD | PROCESS | NOLOCK}
LOCKMODE | Lock used | Description |
---|---|---|
THREAD [default] | high-performance thread read-write lock | For single process multiple threads access. |
PROCESS | file read-write lock | For multiple processes multiple threads access. |
NOLOCK | no lock | For test/diag purpose only. |
Note
'[path]/db_name'
is only valid for embedded database. db_options
are default values for new created tables and you can use table_options
to overwrite these default values.
Open Database¶
OPEN DATABASE {db_name | '[path/]db_name'} [dbg_option] ...
dbg_option:
FLUSHMODE = {ASYNC | SYNC | NOSYNC}
| LOCKMODE = {THREAD | PROCESS | NOLOCK}
Note
This command can only be used for embedded database. dbg_option is only valid for current session and only for debug purpose.
Close Database¶
Note
This command can only be used for embedded database.
Drop Database¶
Use Database¶
Show Databases¶
XDB> show DATABASES ;
+----------+--------+-----------+
| database | engine | data_path |
+----------+--------+-----------+
| system | | |
| memory | | |
+----------+--------+-----------+
2 rows in set (0.012 ms)