Joins

A join is a way of combining columns from one on more tables, using a condition that links the tables.

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SQL: Compare Two Tables for Differences in Data

How to compare two tables that share the same structure, to identify data differences between the two tables: missing rows, extra rows, or mismatch in attribute values.

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INNER JOIN and OUTER JOIN Explained

Overview of INNER JOIN and OUTER JOIN in Oracle, with examples, memory aids and a further drilldown of INNER JOIN and OUTER JOIN types.

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DISTINCT Keyword in Oracle

DISTINCT and How NOT To Use It

The DISTICT keyword placed next to SELECT restricts the result to unique rows from a query. DISTINCT is also a much abused keyword, often used as a quick fix to bad queries. Take this example from Oracle Applications:

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Scalar Subquery

Scalar Subquery

A subquery in the SELECT clause of the main query is called a scalar subquery. This is a single row, single column query, which looks just like a column or function in the SELECT clause. The structure is:

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