- INNER, OUTER, cross, natural, and self joins.
- Returns only matching records from each joined table.
- dbname.tablename AS a
- LEFT, RIGHT, FULL, right excluding, and left excluding.
- Includes all rows from the right table that don't match records in the left table.
- Associates columns of the same name in the joined tables with each other. It's similar to an inner join or left outer join.
- It returns a combination of every row from two tables.
- UNION removes duplicates and UNION ALL doesn't.
- By using DISTINCT in SELECT clause and an INNER JOIN.
- By ensuring you use the indexes that are on the tables or by adding indexes to the tables.
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