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Tag: inner-join

Update columns based on calculation

My table looks like this: I have a list of id’s connected to datestamps. I can manage to calculate the difference between their latest and first entry as follows: However, I am unsure how I can update my table to reflect these calculations. What I want is the following: Answer In MySQL, you can self-join: I would not necessarily recommend

subquery shows more that one row group by

I am trying to get the data for the best 5 customers in a railway reservation system. To get that, I tried getting the max value by summing up their fare every time they make a reservation. Here is the code. this throws the error:[21000][1242] Subquery returns more than 1 row If I remove the group by from the subquery

SELECT NOT IN with multiple columns in subquery

Regarding the statement below, sltrxid can exist as both ardoccrid and ardocdbid. I’m wanting to know how to include both in the NOT IN subquery. Answer I would recommend not exists: Note that I changed the table aliases to things that are more meaningful. I would strongly recommend prefixing the column names with the table they belong to, so the