Using the NVL Function |
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The Null ValueAn empty field is said to contain NULL. A NULL is defined as a value that is unavailable, unassigned, unknown, or inapplicable. A NULL is not the same as a zero or a space. Zero is a number and a space is a character. The COMMISSION_PCT column in the EMPLOYEES table contains NULLs. Columns of any data type can contain NULLs unless the column was defined as NOT NULL when the table was created. Also, primary key columns cannot have NULLs. The NVL FunctionYou can use the NVL function to convert a NULL to another value. NVL ( expr1, expr2)
The NATURAL JOIN clause and the USING clause are mutually exclusive. They cannot be used in the same SELECT statement. Use the USING clause if your tables contain more than one column whose names match to explicitly identify the name of the columns that you want to join.
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