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Oracle connection query

Oracle join query includes internal association (inner jion) and external association (outer join), in which external relevance is divided into left outer association (left outer join), right outer association (right outer join) and full outer association (full outer join), which can be represented by (+).

Internal connection

Join within Oracle: two tables are associated internally through a field through which the query results are rows of data matched by relational operators. These can include:

1. Equivalent join: use the equals sign (=) operator in the join condition to compare the column values of the connected columns, and all the columns in the joined table are listed in the query results.

2. Unequal join: compare the column values of the connected column with other comparison operators other than the equal operator in the join condition, including >, > =,!

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