Sql queries for updating a column
The general SQL is something like this: The trouble is that I get no results updated with the above.
If I modify the JOIN predicate so only one column instead of several columns is joined, everything works fine (albeit not correctly), but I need it to be joined or where'd on several columns.
It is certainly more succinct where Celko’s book contains anecdotes and reasoning behind each rule as thoughtful prose.
It is easy to include this guide in Markdown format as a part of a project’s code base or reference it here for anyone on the project to freely read—much harder with a physical book.
You say you have 2 tables, but you show the definition for 3 tables. AND (C.column1, C.column2, C.column3) IS DISTINCT FROM (A.column1, B.column2, A.column1 B.column2) clause is optional to avoid empty updates that would not change anything (but still write a new row version at full cost).
You say you are attempting to create a table, but show the code for updating rows within an existing table. If your intent is to insert rows from A B into C, you likely want to use an INSERT statement. @ypercube already gave a basic explanation in his comment.
Does anyone see how the JOIN clause (or maybe a equivalent WHERE clause) could be written to get aggregate data with the multiple columns matching?