Sams Teach Yourself SQL in 24 Hours, Third Edition By Ronald R. Plew, Ryan K. Stephens
Table of Contents
Hour 13. Joining Tables in Queries
Q&A
Q1:
When joining tables, must they be joined in the same order that they appear in the FROM clause?
A1:
No, they do not have to appear in the same order; however, performance benefits may be experienced depending on the order of tables in the FROM clause and the order that tables are joined.
Q2:
When using a BASE TABLE to join unrelated tables, must I select any columns from the base table?
A2:
No, the use of a BASE TABLE to join unrelated tables does not mandate columns for selection from the base table.
Q3:
Can I join on more than one column between tables?
A3:
Yes, some queries may require you to join on more than one column per table to provide a complete relationship between rows of data in the joined tables.
