The sign function of SQL

The SQL sign function returns -1, 0, or 1 when the corresponding field of a table in the database is numeric and the value is negative, 0, or positive.

For example

          SELECT sign (dailyChange) PriceChange from PRICE where DATE = to_date('03/21/2014', 'MM/dd/yyyy');

If on March 21, 2014, the price was decreased, that is the dailyChange is a negative value, the output of the query is -1; if the price did not change, the output is 0; and if the price was increased, the output of the query is 1.

Another example

          SELECT sign(TotalCharge - Paid) OweMoney from ORDER where customer_ID = 5588;

If the customer paid less than the total charge, the output is 1; if the customer paid the exact amount of total charge, the output is 0; and if the customer paid more than the total charge, the output is -1.

References
1. ORACLE/PLSQL: SIGN FUNCTION

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