homework-jianmu/docs-en/12-taos-sql/12-keywords.md

title
Keywords

There are about 200 keywords reserved by TDengine, they can't be used as the name of database, STable or table with either upper case, lower case or mixed case.

Keywords List

ABORT	CREATE	IGNORE	NULL	STAR
ACCOUNT	CTIME	IMMEDIATE	OF	STATE
ACCOUNTS	DATABASE	IMPORT	OFFSET	STATEMENT
ADD	DATABASES	IN	OR	STATE_WINDOW
AFTER	DAYS	INITIALLY	ORDER	STORAGE
ALL	DBS	INSERT	PARTITIONS	STREAM
ALTER	DEFERRED	INSTEAD	PASS	STREAMS
AND	DELIMITERS	INT	PLUS	STRING
AS	DESC	INTEGER	PPS	SYNCDB
ASC	DESCRIBE	INTERVAL	PRECISION	TABLE
ATTACH	DETACH	INTO	PREV	TABLES
BEFORE	DISTINCT	IS	PRIVILEGE	TAG
BEGIN	DIVIDE	ISNULL	QTIME	TAGS
BETWEEN	DNODE	JOIN	QUERIES	TBNAME
BIGINT	DNODES	KEEP	QUERY	TIMES
BINARY	DOT	KEY	QUORUM	TIMESTAMP
BITAND	DOUBLE	KILL	RAISE	TINYINT
BITNOT	DROP	LE	REM	TOPIC
BITOR	EACH	LIKE	REPLACE	TOPICS
BLOCKS	END	LIMIT	REPLICA	TRIGGER
BOOL	EQ	LINEAR	RESET	TSERIES
BY	EXISTS	LOCAL	RESTRICT	UMINUS
CACHE	EXPLAIN	LP	ROW	UNION
CACHELAST	FAIL	LSHIFT	RP	UNSIGNED
CASCADE	FILE	LT	RSHIFT	UPDATE
CHANGE	FILL	MATCH	SCORES	UPLUS
CLUSTER	FLOAT	MAXROWS	SELECT	USE
COLON	FOR	MINROWS	SEMI	USER
COLUMN	FROM	MINUS	SESSION	USERS
COMMA	FSYNC	MNODES	SET	USING
COMP	GE	MODIFY	SHOW	VALUES
COMPACT	GLOB	MODULES	SLASH	VARIABLE
CONCAT	GRANTS	NCHAR	SLIDING	VARIABLES
CONFLICT	GROUP	NE	SLIMIT	VGROUPS
CONNECTION	GT	NONE	SMALLINT	VIEW
CONNECTIONS	HAVING	NOT	SOFFSET	VNODES
CONNS	ID	NOTNULL	STable	WAL
COPY	IF	NOW	STableS	WHERE
_C0	_QSTART	_QSTOP	_QDURATION	_WSTART
_WSTOP	_WDURATION	_ROWTS

Explanations

TBNAME

TBNAME can be considered as a special tag, which represents the name of the subtable, in a STable.

Get the table name and tag values of all subtables in a STable.

SELECT TBNAME, location FROM meters;

Count the number of subtables in a STable.

SELECT COUNT(TBNAME) FROM meters;

Only filter on TAGS can be used in WHERE clause in the above two query statements.

taos> SELECT TBNAME, location FROM meters;
             tbname             |            location            |
==================================================================
 d1004                          | California.SanFrancisco        |
 d1003                          | California.SanFrancisco        |
 d1002                          | California.LosAngeles          |
 d1001                          | California.LosAngeles          |
Query OK, 4 row(s) in set (0.000881s)

taos> SELECT COUNT(tbname) FROM meters WHERE groupId > 2;
     count(tbname)     |
========================
                     2 |
Query OK, 1 row(s) in set (0.001091s)

_QSTART/_QSTOP/_QDURATION

The start, stop and duration of a query time window.

_WSTART/_WSTOP/_WDURATION

The start, stop and duration of aggegate query by time window, like interval, session window, state window.

_c0/_ROWTS

_c0 is equal to _ROWTS, it means the first column of a table or STable.