| Base of difference | Inner Join | Outer Join |
| Variant | When we say about the Inner join there is no variants | And when we say about the variant in Outer join we have two variant that are Left outer or right outer join. |
| Records | When we say about the records here we have common records from both the tables and one condition is there is there must have some common Id. | And when we say about the Outer join we have all entries from the table are taken and there we not required the common Id. |
| Rows or entries | All the rows or entries will have values as it is taken from the tables with common entries. | All the rows or entries will not have values and return null value as tables with common ID is not necessary. |
| Use of optimizer | We can use optimizer in inner join as it gives many options. | And when we say about the optimizer it is limited as the joins take all the entries and its usage is not feasible. |
| Used when | We use inner join when we have the related data entry should exist as per the customer requirement or database design, use inner join. | We use outer join when we have a related data entry existence is not necessary, as per the customer requirement or database design, use outer join. |
| Option | Inner join is the common join and is used judiciously. The results provided have least entries and in most cases, will be able to update the requirement of the user. | Outer join has many options such as left and right join and hence its usage must be monitored and the results must be checked thoroughly. |
| Performance | When we say about the performance Inner join are much slower which is not up to mark. | When we say about the Outer joins especially left outer joins are faster and perform well in most cases. |
| Condition | When we say about the Inner join a condition is given in the inner join query and it is necessary to satisfy the same. | When we say about the Outer join a condition is not given in the outer join query and they need not match any conditions. |
| Output | If the rows in table A does not have any matching entries in table B, then those entries are not considered for output in the inner join. | If the rows in table A does not have any matching entries in table B, then the output will return null values. |
| Result state | In Inner Join if the rows in table A does not have any matching entries in table B, then the output will return null values. | In Outer join if there is a match in tables, it will check either the condition whether it is given for left or right tables. If the condition is given, the entry is considered accordingly. If no conditions are given, then the full outer join is the output for the same. |