That is: select a. MySQL INNER JOINS return all rows from multiple tables where the join condition is met. INNER JOIN (simple join) Chances are, you've already written a statement that uses a MySQL INNER JOIN. INNER JOINS only return rows that meet the given criteria. It is the most common type of join. Basically I'm trying to select everything from Table 1, but in the results, I need to show the Username rather than the User ID, and I know I'd have to use an INNER JOIN query to select the Username from Table 2. The unmatched rows are returned with the NULL keyword. OUTER JOINS can also return rows where no matches have been found. An SQL join clause - corresponding to a join operation in relational algebra - combines columns from one or more tables in a relational database.It creates a set that can be saved as a table or used as it is. MySQL Inner Join is one of the Join Type, which returns the records or rows present in both tables If there is at least one match between columns. This diagram has one major problem, which is that it completely ignores the difference between semi-joins and joins. MySQL RIGHT OUTER JOIN (or sometimes called RIGHT JOIN) MySQL Inner JOIN (Simple Join) The MySQL INNER JOIN is used to return all rows from multiple tables where the join condition is satisfied. The major JOIN types include Inner, Left Outer, Right Outer, Cross JOINS etc. A JOIN is a means for combining columns from one (self-join) or more tables by using values common to each. The frequently used clause in JOIN operations is "ON". * from a inner join b on a.id = b.id vs. select a. * from a where id in (select id from b).That is because SQL joins are NOT the intersection of two sets- the join can be one->one, one->many, or many->many. Regards, Tom. Or, we can simply say, MySQL Inner Join returns the rows (or records) present in both tables as long as the condition after the ON Keyword is TRUE. It is the most common type of join.