PostgreSQL – JOINS The PostgreSQL Joins clause is used to combine records from two or more tables in a database. A JOIN is a means for combining fields from two tables by using values common to each. Join Types in PostgreSQL are − The CROSS JOIN The INNER JOIN The LEFT OUTER JOIN The RIGHT […]
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PostgreSQL – UNIONS Clause The PostgreSQL UNION clause/operator is used to combine the results of two or more SELECT statements without returning any duplicate rows. To use UNION, each SELECT must have the same number of columns selected, the same number of column expressions, the same data type, and have them in the same order […]
PostgreSQL – NULL Values The PostgreSQL NULL is the term used to represent a missing value. A NULL value in a table is a value in a field that appears to be blank. A field with a NULL value is a field with no value. It is very important to understand that a NULL value […]