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CritasWang merged 3 commits into from
Aug 28, 2025
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Add support version to minby maxby #784

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ce00b72
fix iotdb enterprise edition to timechodb
leto-b Jun 10, 2025
570b4bc
add support version to minby and maxby
leto-b Jun 10, 2025
ac878d8
remove other changes
leto-b Jun 12, 2025
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228 changes: 208 additions & 20 deletions src/UserGuide/V1.3.x/SQL-Manual/Function-and-Expression.md
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Original file line number Diff line number Diff line change
Expand Up @@ -539,6 +539,12 @@ The aggregate functions supported by IoTDB are as follows:
| SUM | Summation. | INT32 INT64 FLOAT DOUBLE | / | DOUBLE |
| COUNT | Counts the number of data points. | All data types | / | INT |
| AVG | Average. | INT32 INT64 FLOAT DOUBLE | / | DOUBLE |
STDDEV | Alias for STDDEV_SAMP. Return the sample standard deviation. | INT32 INT64 FLOAT DOUBLE | / | DOUBLE |
| STDDEV_POP | Return the population standard deviation. | INT32 INT64 FLOAT DOUBLE | / | DOUBLE |
| STDDEV_SAMP | Return the sample standard deviation. | INT32 INT64 FLOAT DOUBLE | / | DOUBLE |
| VARIANCE | Alias for VAR_SAMP. Return the sample variance. | INT32 INT64 FLOAT DOUBLE | / | DOUBLE |
| VAR_POP | Return the population variance. | INT32 INT64 FLOAT DOUBLE | / | DOUBLE |
| VAR_SAMP | Return the sample variance. | INT32 INT64 FLOAT DOUBLE | / | DOUBLE |
| EXTREME | Finds the value with the largest absolute value. Returns a positive value if the maximum absolute value of positive and negative values is equal. | INT32 INT64 FLOAT DOUBLE | / | Consistent with the input data type |
| MAX_VALUE | Find the maximum value. | INT32 INT64 FLOAT DOUBLE | / | Consistent with the input data type |
| MIN_VALUE | Find the minimum value. | INT32 INT64 FLOAT DOUBLE | / | Consistent with the input data type |
Expand All @@ -549,29 +555,11 @@ The aggregate functions supported by IoTDB are as follows:
| COUNT_IF | Find the number of data points that continuously meet a given condition and the number of data points that meet the condition (represented by keep) meet the specified threshold. | BOOLEAN | `[keep >=/>/=/!=/</<=]threshold`：The specified threshold or threshold condition, it is equivalent to `keep >= threshold` if `threshold` is used alone, type of `threshold` is `INT64` `ignoreNull`：Optional, default value is `true`；If the value is `true`, null values are ignored, it means that if there is a null value in the middle, the value is ignored without interrupting the continuity. If the value is `true`, null values are not ignored, it means that if there are null values in the middle, continuity will be broken | INT64 |
| TIME_DURATION | Find the difference between the timestamp of the largest non-null value and the timestamp of the smallest non-null value in a column | All data Types | / | INT64 |
| MODE | Find the mode. Note: 1.Having too many different values in the input series risks a memory exception; 2.If all the elements have the same number of occurrences, that is no Mode, return the value with earliest time; 3.If there are many Modes, return the Mode with earliest time. | All data Types | / | Consistent with the input data type |
| STDDEV | Calculate the overall standard deviation of the data. Note:<br> Missing points, null points and `NaN` in the input series will be ignored.| INT32 INT64 FLOAT DOUBLE | / | DOUBLE |
| COUNT_TIME | The number of timestamps in the query data set. When used with `align by device`, the result is the number of timestamps in the data set per device. | All data Types, the input parameter can only be `*` | / | INT64 |
| MAX_BY | MAX_BY(x, y) returns the value of x corresponding to the maximum value of the input y. MAX_BY(time, x) returns the timestamp when x is at its maximum value. <br> Note: Supported from version V1.3.2 | The first input x can be of any type, while the second input y must be of type INT32, INT64, FLOAT, DOUBLE, STRING, TIMESTAMP or DATE. | / | Consistent with the data type of the first input x. |
| MIN_BY | MIN_BY(x, y) returns the value of x corresponding to the minimum value of the input y. MIN_BY(time, x) returns the timestamp when x is at its minimum value. <br> Note: Supported from version V1.3.2 | The first input x can be of any type, while the second input y must be of type INT32, INT64, FLOAT, DOUBLE, STRING, TIMESTAMP or DATE. | / | Consistent with the data type of the first input x. |


### COUNT

#### example

```sql
select count(status) from root.ln.wf01.wt01;
```
Result:

```
+-------------------------------+
|count(root.ln.wf01.wt01.status)|
+-------------------------------+
| 10080|
+-------------------------------+
Total line number = 1
It costs 0.016s
```

### COUNT_IF

#### Grammar
Expand Down Expand Up @@ -800,6 +788,206 @@ Result
> 3. Count_time aggregation used with having statement is not supported, and count_time aggregation can not appear in the having statement.
> 4. Count_time does not support use with group by level, group by tag.




### MAX_BY

#### Function Definition
`max_by(x, y)`: Returns the value of x at the timestamp where y reaches its maximum.

- `max_by` must have two input parameters x and y.
- The first input can be the time keyword. `max_by(time, x)` returns the timestamp when x reaches its maximum value.
- Returns null if x is null at the timestamp where y is maximum.
- If y achieves its maximum at multiple timestamps, returns the x value at the smallest timestamp among them.
- Aligns with IoTDB's `max_value`: Only supports INT32, INT64, FLOAT, DOUBLE as y input. Supports all six data types as x input.
- Inputs x and y cannot be literal values.

#### Syntax
```sql
select max_by(x, y) from root.sg
select max_by(time, x) from root.sg
```

#### Examples

##### Raw Data
```sql
IoTDB> select * from root.test
+-----------------------------+-----------+-----------+
| Time|root.test.a|root.test.b|
+-----------------------------+-----------+-----------+
|1970-01-01T08:00:00.001+08:00| 1.0| 10.0|
|1970-01-01T08:00:00.002+08:00| 2.0| 10.0|
|1970-01-01T08:00:00.003+08:00| 3.0| 3.0|
|1970-01-01T08:00:00.004+08:00| 10.0| 10.0|
|1970-01-01T08:00:00.005+08:00| 10.0| 12.0|
|1970-01-01T08:00:00.006+08:00| 6.0| 6.0|
+-----------------------------+-----------+-----------+
```
##### Query Examples
Get timestamp corresponding to maximum value:
```sql
IoTDB> select max_by(time, a), max_value(a) from root.test
+-------------------------+------------------------+
|max_by(Time, root.test.a)| max_value(root.test.a)|
+-------------------------+------------------------+
| 4| 10.0|
+-------------------------+------------------------+
```

Get b value when a is maximum:
```sql
IoTDB> select max_by(b, a) from root.test
+--------------------------------+
|max_by(root.test.b, root.test.a)|
+--------------------------------+
| 10.0|
+--------------------------------+
```

With expressions:
```sql
IoTDB> select max_by(b + 1, a * 2) from root.test
+----------------------------------------+
|max_by(root.test.b + 1, root.test.a * 2)|
+----------------------------------------+
| 11.0|
+----------------------------------------+
```

With GROUP BY TIME clause:
```sql
IoTDB> select max_by(b, a) from root.test group by ([0,7),4ms)
+-----------------------------+--------------------------------+
| Time|max_by(root.test.b, root.test.a)|
+-----------------------------+--------------------------------+
|1970-01-01T08:00:00.000+08:00| 3.0|
+-----------------------------+--------------------------------+
|1970-01-01T08:00:00.004+08:00| 10.0|
+-----------------------------+--------------------------------+
```

With HAVING clause:
```sql
IoTDB> select max_by(b, a) from root.test group by ([0,7),4ms) having max_by(b, a) > 4.0
+-----------------------------+--------------------------------+
| Time|max_by(root.test.b, root.test.a)|
+-----------------------------+--------------------------------+
|1970-01-01T08:00:00.004+08:00| 10.0|
+-----------------------------+--------------------------------+
```
With ORDER BY clause:
```sql
IoTDB> select max_by(b, a) from root.test group by ([0,7),4ms) order by time desc
+-----------------------------+--------------------------------+
| Time|max_by(root.test.b, root.test.a)|
+-----------------------------+--------------------------------+
|1970-01-01T08:00:00.004+08:00| 10.0|
+-----------------------------+--------------------------------+
|1970-01-01T08:00:00.000+08:00| 3.0|
+-----------------------------+--------------------------------+
```

### MIN_BY
#### Function Definition
`min_by(x, y)`: Returns the value of x at the timestamp where y reaches its minimum.

- `min_by` must have two input parameters x and y.
- The first input can be the time keyword. `min_by(time, x)` returns the timestamp when x reaches its minimum value.
- Returns null if x is null at the timestamp where y is minimum.
- If y achieves its minimum at multiple timestamps, returns the x value at the smallest timestamp among them.
- Aligns with IoTDB's `min_value`: Only supports INT32, INT64, FLOAT, DOUBLE as y input. Supports all six data types as x input.
- Inputs x and y cannot be literal values.

#### Syntax
```sql
select min_by(x, y) from root.sg
select min_by(time, x) from root.sg
```

#### Examples

##### Raw Data
```sql
IoTDB> select * from root.test
+-----------------------------+-----------+-----------+
| Time|root.test.a|root.test.b|
+-----------------------------+-----------+-----------+
|1970-01-01T08:00:00.001+08:00| 4.0| 10.0|
|1970-01-01T08:00:00.002+08:00| 3.0| 10.0|
|1970-01-01T08:00:00.003+08:00| 2.0| 3.0|
|1970-01-01T08:00:00.004+08:00| 1.0| 10.0|
|1970-01-01T08:00:00.005+08:00| 1.0| 12.0|
|1970-01-01T08:00:00.006+08:00| 6.0| 6.0|
+-----------------------------+-----------+-----------+
```
##### Query Examples
Get timestamp corresponding to minimum value:
```sql
IoTDB> select min_by(time, a), min_value(a) from root.test
+-------------------------+------------------------+
|min_by(Time, root.test.a)| min_value(root.test.a)|
+-------------------------+------------------------+
| 4| 1.0|
+-------------------------+------------------------+
```

Get b value when a is minimum:
```sql
IoTDB> select min_by(b, a) from root.test
+--------------------------------+
|min_by(root.test.b, root.test.a)|
+--------------------------------+
| 10.0|
+--------------------------------+
```

With expressions:
```sql
IoTDB> select min_by(b + 1, a * 2) from root.test
+----------------------------------------+
|min_by(root.test.b + 1, root.test.a * 2)|
+----------------------------------------+
| 11.0|
+----------------------------------------+
```

With GROUP BY TIME clause:
```sql
IoTDB> select min_by(b, a) from root.test group by ([0,7),4ms)
+-----------------------------+--------------------------------+
| Time|min_by(root.test.b, root.test.a)|
+-----------------------------+--------------------------------+
|1970-01-01T08:00:00.000+08:00| 3.0|
+-----------------------------+--------------------------------+
|1970-01-01T08:00:00.004+08:00| 10.0|
+-----------------------------+--------------------------------+
```

With HAVING clause:
```sql
IoTDB> select min_by(b, a) from root.test group by ([0,7),4ms) having max_by(b, a) > 4.0
+-----------------------------+--------------------------------+
| Time|min_by(root.test.b, root.test.a)|
+-----------------------------+--------------------------------+
|1970-01-01T08:00:00.004+08:00| 10.0|
+-----------------------------+--------------------------------+
```

With ORDER BY clause:
```sql
IoTDB> select min_by(b, a) from root.test group by ([0,7),4ms) order by time desc
+-----------------------------+--------------------------------+
| Time|min_by(root.test.b, root.test.a)|
+-----------------------------+--------------------------------+
|1970-01-01T08:00:00.004+08:00| 10.0|
+-----------------------------+--------------------------------+
|1970-01-01T08:00:00.000+08:00| 3.0|
+-----------------------------+--------------------------------+
```


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