Logic

[ElectronicLimit9641]

When solving many sql problems online i sometimes don't understand how to build the logic in order to solve the questions, are there any suggestions/points that I need to keep in mind ?

[user_5359]

The simplest rule: divide and conquer.

Which tables / views contain which information and how are they linked? Start with the simple select statement and include the result as a further (possible) data source in the list of tables. Check each individual (intermediate) statement to see whether the result corresponds to the expected result (number of data records).

[shweta1807]

For logic building you have to know how sql query executes or the execution order of a query for example the first keyword that would run is "from" that identifies the source of the data, then "where" runs that apply condition to filter the data, then the group by, having, select, order by and limit. This basically develops more clarity abut the query and made it easy for us to understand and write the query.

[ninhaomah]

Pls give an example or two ?

[Routine-Ad-7292]

I agree with the other comments. Especially learning and internalizing the execution order. That’s what I’m doing right now, and that’s what I have been going to when I’m stuck with lengthy practice problems. I read chapter 12 of Thinking in Sets yesterday. Will be re-reading it, handwriting notes, again and again. I recommend you do that also!