# SQL statement to calculate difference between specified value and all other values of one field **URL:** \ **Category:** InfluxDB 2\ **Created:** [April 7, 2019, 12:36am UTC](https://community.influxdata.com/t/sql-statement-to-calculate-difference-between-specified-value-and-all-other-values-of-one-field/9346 "2019-04-07T00:36:57Z")\ **Posts on this page:** 1\ **Page:** 1
**Author:** ![Michael\_Reis](https://sea1.discourse-cdn.com/flex023/user_avatar/community.influxdata.com/michael_reis/32/2717_2.png) [@Michael\_Reis](https://community.influxdata.com/u/Michael_Reis)\ **Post date:** [April 7, 2019, 12:36am UTC](https://community.influxdata.com/t/sql-statement-to-calculate-difference-between-specified-value-and-all-other-values-of-one-field/9346/1 "2019-04-07T00:36:57Z")
I’m trying to come up with a query that’s similar to the InfluxDB Difference function, except that rather than calculating the difference between subsequent field values, it would calculate the difference with respect to a specific field value. I’m using InfluxDB to store performance test statistics, and I’d like to see the difference of each Response Time value with respect to a baseline Response Time value. Say I had a measurement consisting of the 2 fields, “Date” and “Resp Time”, and the data looks like this: | Date | Resp Time | | 1/1/2019 | 4 | | 1/2/2019 | 7 | | 1/3/2019 | 3 | | 1/4/2019 | 9 | | 1/5/2019 | 2 | The 1/3/2019 row contains the Resp Time value that I’d like to compare each of the other Resp Time values to. I would like an output that looks something like this: | Date | Resp Time | | Difference | | 1/1/2019 | 4 | | 1 | | 1/2/2019 | 7 | | 4 | | 1/3/2019 | 3 | | 0 | | 1/4/2019 | 9 | | 6 | | 1/5/2019 | 2 | | -1 | I was thinking of a query like this but I don’t think I can reference different table aliases in the Select portion of an InfluxDB query: SELECT t1.Date, t1.RespTime, t1.RespTime-t2.RespTime AS Difference FROM Table1 AS t1, Table1 AS t2 WHERE t2.Date=“1/3/2019” Any thoughts would be much appreciated.