TAG data UPDATE WHERE/SET constraints

TAG data UPDATE requires an explicit target scope. WHERE must contain both tag selection and BASETIME predicates, and SET can target only actual data columns.

Supported since Machbase 8.7.0

SET Restrictions

Column role	SET allowed	Description
Data column	Yes	value and auxiliary numeric/string columns
SUMMARIZED data column	Yes	Changes source TAG row values
BASETIME column	No	Time-axis column cannot change
PRIMARY KEY column (name)	No	Tag name cannot change
Metadata column	No	Use UPDATE … METADATA separately
Hidden/system column	No	Internal columns are not SET targets

SET expressions allow constants, bind variables, arithmetic/string/CASE expressions without existing-row references, supported conversion functions, and NULL. Existing-row column references, subqueries, and aggregates are unsupported on the right-hand side.

WHERE Restrictions

UPDATE table_name
   SET col = expr
 WHERE name = 'tag-name'
   AND time >= TO_DATE('2026-07-01', 'YYYY-MM-DD');

WHERE predicate	Supported
`name = '...'`	Yes
`name = ?`, `name = :tag_name`	Yes
`? = name`, `:tag_name = name`	Yes
`name IN ('...', '...')`	Yes
`name LIKE '...'`	Yes
`time = t1`	Yes
`time = ?`, `time = :base_time`	Yes
`? = time`, `:base_time = time`	Yes
`time BETWEEN t1 AND t2`	Yes
`time >= t1 AND time < t2`	Yes
`time >= ? AND time < ?`	Yes
One-sided time predicate	Yes
Data-column predicate	Yes
No tag selector	No
No time predicate	No
OR	No
IN (SELECT …)	No
Tag/axis column wrapped in a function or expression	No

Use bind parameters only in predicate value positions. Markers cannot replace tag-name or BASETIME column identifiers, and both tag selection and time predicates remain mandatory. Reexecution selects targets using newly bound values; no match succeeds with 0 affected rows.

For NAME/TIME parameter metadata and SDK APIs, see Bind Parameters in TAG Data UPDATE and Named Bind Parameters.

Metadata UPDATE

UPDATE table_name METADATA
   SET meta_col = value
 WHERE condition;

Metadata UPDATE modifies the tag-attribute area. Its syntax and targets differ from TAG data UPDATE, which modifies data columns in actual time-series rows.

Checking Column Roles

Use DESC to inspect column attributes.

DESC sensor_tag;

Alternatively, query column FLAG values in system tables.

SELECT NAME, TYPE, FLAG
  FROM M$SYS_COLUMNS
 WHERE TABLE_ID = (
     SELECT ID FROM M$SYS_TABLES WHERE NAME = 'SENSOR_TAG'
 );

FLAG value	Meaning
134217728	Tag Name
16777216	Base Time / Base Distance
33554432	Summarized
67108864	Metadata

Error Examples

-- Error: BASETIME column used as a SET target
UPDATE sensor_tag
   SET time = TO_DATE('2026-07-01', 'YYYY-MM-DD')
 WHERE name = 'TEMP-01'
   AND time >= TO_DATE('2026-07-01', 'YYYY-MM-DD');

-- Error: missing time predicate
UPDATE sensor_tag
   SET value = 0.0
 WHERE name = 'TEMP-01';

-- Error: OR predicate
UPDATE sensor_tag
   SET value = 0.0
 WHERE name = 'TEMP-01'
    OR name = 'TEMP-02';