**Description**: The greatest _k_ values of a specific column in a table or STable. If a value has multiple occurrences in the column but counting all of them in will exceed the upper limit _k_, then a part of them will be returned randomly.
**Return value type**: Same as the column being operated
**Return value type**: Same as the column being operated upon
**Applicable column types**: Data types except for timestamp, binary, nchar and bool
**Description**: The least _k_ values of a specific column in a table or STable. If a value has multiple occurrences in the column but counting all of them in will exceed the upper limit _k_, then a part of them will be returned randomly.
**Return value type**: Same as the column being operated
**Return value type**: Same as the column being operated upon
**Applicable column types**: Data types except for timestamp, binary, nchar and bool
-`INTERP` is used to get the value that matches the specified time slice from a column. If no such value exists an interpolation value will be returned based on `FILL` parameter.
- The input data of `INTERP` is the value of the specified column, `where` can be used to filter the original data. If no `where` condition is specified then all original data is the input.
- The input data of `INTERP` is the value of the specified column and a `where` clause can be used to filter the original data. If no `where` condition is specified then all original data is the input.
- The output time range of `INTERP` is specified by `RANGE(timestamp1,timestamp2)` parameter, with timestamp1<=timestamp2. timestamp1 is the starting point of the output time range and must be specified. timestamp2 is the ending point of the output time range and must be specified. If `RANGE` is not specified, then the timestamp of the first row that matches the filter condition is treated as timestamp1, the timestamp of the last row that matches the filter condition is treated as timestamp2.
- The number of rows in the result set of `INTERP` is determined by the parameter `EVERY`. Starting from timestamp1, one interpolation is performed for every time interval specified `EVERY` parameter. If `EVERY` parameter is not used, the time windows will be considered as no ending timestamp, i.e. there is only one time window from timestamp1.
- Interpolation is performed based on `FILL` parameter. No interpolation is performed if `FILL` is not used, that means either the original data that matches is returned or nothing is returned.
taos> SELECT INTERP(current) FROM t1 where ts >= '2017-07-14 17:00:00' and ts <= '2017-07-14 20:00:00' RANGE('2017-7-14 18:00:00','2017-7-14 19:00:00') EVERY(5s) FILL(LINEAR);
```
### INTERP [Prior to version 2.3.1]
### INTERP [Since version 2.0.15.0]
```
SELECT INTERP(field_name) FROM { tb_name | stb_name } WHERE ts='timestamp' [FILL ({ VALUE | PREV | NULL | LINEAR | NEXT})];
...
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@@ -566,7 +566,7 @@ SELECT INTERP(field_name) FROM { tb_name | stb_name } WHERE ts='timestamp' [FILL
**Description**: The value of a specific column that matches the specified time slice
**Return value type**: Same as the column being operated
**Return value type**: Same as the column being operated upon
**Applicable column types**: Numeric data type
...
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@@ -574,7 +574,6 @@ SELECT INTERP(field_name) FROM { tb_name | stb_name } WHERE ts='timestamp' [FILL
**More explanations**:
- It can be used from version 2.0.15.0
- Time slice must be specified. If there is no data matching the specified time slice, interpolation is performed based on `FILL` parameter. Conditions such as tags or `tbname` can be used `Where` clause can be used to filter data.
- The timestamp specified must be within the time range of the data rows of the table or STable. If it is beyond the valid time range, nothing is returned even with `FILL` parameter.
-`INTERP` can be used to query only single time point once. `INTERP` can be used with `EVERY` to get the interpolation value every time interval.
**Description**: The different of each row with its previous row for a specific column. `ignore_negative` can be specified as 0 or 1, the default value is 1 if it's not specified. `1` means negative values are ignored.
**Return value type**: Same as the column being operated
**Return value type**: Same as the column being operated upon
**Applicable column types**: Data types except for timestamp, binary, nchar and bool
- It is available from version 2.1.3.0, the number of result rows is the number of total rows in the time range subtracted by one, no output for the first row.
- It is available since version 2.1.3.0, the number of result rows is the number of total rows in the time range subtracted by one, no output for the first row.
- It can be used together with `GROUP BY tbname` against a STable.
**Examples**:
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@@ -715,7 +714,7 @@ Query OK, 1 row(s) in set (0.000836s)
SELECT CEIL(field_name) FROM { tb_name | stb_name } [WHERE clause];
```
**Description**: The round up value of a specific column
**Description**: The rounded up value of a specific column
**Return value type**: Same as the column being used
