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An aggregate function that returns the first value of a set of input values, defined as the value associated with the minimum time.
FIRST (value[, time]);
DATETIME
, DATETIME(6)
, TIMESTAMP
, TIMESTAMP(6)
. If no time expression is specified, then the SERIES TIMESTAMP
is used to defined the time order. Only one SERIES TIMESTAMP
can appear in tables used in the query if the time
argument is omitted.The first value of a set of input rows, as ordered by the time column.
SERIES TIMESTAMP
columns involved, or one is needed due to omission of the time
argument but none is present. For example, if more than one table in the FROM
clause has a SERIES TIMESTAMP
, then it becomes ambiguous which timestamp to use. Hence, the SERIES TIMESTAMP
to be used must be specified in the second argument of the FIRST
function.The following examples display the use of FIRST
function.
CREATE TABLE table1 (a INT, b DATETIME SERIES TIMESTAMP);
INSERT INTO table1 values (1, "2019-03-14 06:28:00"), (2, "2019-04-14 06:28:00"), (3, "2018-03-14 06:28:00");
SELECT FIRST (a) FROM table1;
+--------------+
| FIRST (a) |
+--------------+
| 3 |
+--------------+
SELECT FIRST (a, b) FROM table1;
****
+--------------+
| FIRST (a, b) |
+--------------+
| 3 |
+--------------+