MONTHS_BETWEEN

Description

Unlike the MONTHS_DIFF function, the MONTHS_BETWEEN function does not ignore the day component and returns a floating-point number representing the actual difference in months, rather than the simple difference in month units displayed on the date.

The MONTHS_BETWEEN function is used to calculate the month difference between two datetime values, returning a floating-point result. This function supports processing DATE and DATETIME types and can control whether the result is rounded through an optional parameter.

This function behaves consistently with Oracle's MONTHS_BETWEEN function.

Syntax

MONTHS_BETWEEN(`<date_or_time_expr1>`, `<date_or_time_expr2>` [, `<round_type>`])

Parameters

Parameter	Description
<date_or_time_expr1>	End date. Supports date/datetime types. For specific datetime and date formats, see datetime conversion and date conversion.
<date_or_time_expr2>	Start date. Supports date/datetime types and strings that conform to datetime formats.
<round_type>	Whether to round the result to the 8th decimal place. Supports true or false. Default is true.

Return Value

Returns the number of months obtained by subtracting <date_or_time_expr2> from <date_or_time_expr1>, of type DOUBLE.

Result = (<date_or_time_expr1>.year - <date_or_time_expr2>.year) * 12 + <date_or_time_expr1>.month - <date_or_time_expr2>.month + (<date_or_time_expr1>.day - <date_or_time_expr2>.day) / 31.0

• When <date_or_time_expr1> or <date_or_time_expr2> is NULL, or both are NULL, returns NULL
• When <round_type> is true, the result is rounded to the 8th decimal place; otherwise, it maintains DOUBLE precision (15 decimal places)
• If <date_or_time_expr1> is earlier than <date_or_time_expr2>, returns a negative value
• Time components (hours, minutes, seconds) do not affect the calculation; only date components (year, month, day) are used

When <date_or_time_expr1> and <date_or_time_expr2> meet the following conditions, the function returns an integer month difference (ignoring fractional parts caused by day differences):

• Both dates are the last day of their respective months (e.g., 2024-01-31 and 2024-02-29)
• Both dates have the same day component (e.g., 2024-01-15 and 2024-03-15)

Examples

--- Month difference between two dates
SELECT MONTHS_BETWEEN('2020-12-26', '2020-10-25') AS result;
+------------+
| result     |
+------------+
| 2.03225806 |
+------------+

--- Including time components (does not affect result)
SELECT MONTHS_BETWEEN('2020-12-26 15:30:00', '2020-10-25 08:15:00') AS result;
+------------+
| result     |
+------------+
| 2.03225806 |
+------------+

--- Disable rounding (preserve original precision)
SELECT MONTHS_BETWEEN('2020-10-25', '2020-12-26', false) AS result;
+---------------------+
| result              |
+---------------------+
| -2.032258064516129  |
+---------------------+

--- Both are month-end dates (special handling, returns integer)
SELECT MONTHS_BETWEEN('2024-02-29', '2024-01-31') AS result;
+--------+
| result |
+--------+
|      1 |
+--------+

--- Same day component (special handling, returns integer)
SELECT MONTHS_BETWEEN('2024-03-15', '2024-01-15') AS result;
+--------+
| result |
+--------+
|      2 |
+--------+

--- Different day components and not month-end
SELECT MONTHS_BETWEEN('2024-02-29', '2024-01-30') AS result;
+------------+
| result     |
+------------+
| 0.96774194 |
+------------+

--- Input is NULL (returns NULL)
SELECT MONTHS_BETWEEN(NULL, '2024-01-01') AS result;
+--------+
| result |
+--------+
| NULL   |
+--------+