Warning
SingleStore 9.0 gives you the opportunity to preview, evaluate, and provide feedback on new and upcoming features prior to their general availability. In the interim, SingleStore 8.9 is recommended for production workloads, which can later be upgraded to SingleStore 9.0.
LAG
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Returns an expression evaluated at some offset before the current row.
If there is no such row returns NULL instead.
Syntax
LAG ( expression [, offset]) OVER (
[PARTITION BY (col | expr), ...]
[ORDER BY (col | expr), ...]
)Arguments
-
expression: any expression.
This may be a column name, the result of another function, or a math operation -
offset: A constant integer that specifies the number of rows before the current row to evaluate the expression.
Defaults to 1 if not specified
Return Type
The result of expression
Examples
CREATE TABLE lag_example (a int, b int);INSERT INTO lag_example VALUES(1,2),(2,2),(3,3),(4,3);
SELECT a, LAG(a) OVER(ORDER BY (a)) FROM lag_example;
+------+---------------------------+
| a | LAG(a) OVER(ORDER BY (a)) |
+------+---------------------------+
| 1 | NULL |
| 2 | 1 |
| 3 | 2 |
| 4 | 3 |
+------+---------------------------+SELECT a, LAG(a,2) OVER(ORDER BY (a)) FROM lag_example;
+------+-----------------------------+
| a | LAG(a,2) OVER(ORDER BY (a)) |
+------+-----------------------------+
| 1 | NULL |
| 2 | NULL |
| 3 | 1 |
| 4 | 2 |
+------+-----------------------------+Last modified: February 16, 2023