COALESCE
Syntax
Purpose
COALESCE
returns the first nonnull expr
in the expression list. You must specify at least two expressions. If all occurrences of expr
evaluate to null, then the function returns null.
Oracle Database uses shortcircuit evaluation. The database evaluates each expr
value and determines whether it is NULL
, rather than evaluating all of the expr
values before determining whether any of them is NULL
.
If all occurrences of expr
are numeric data type or any nonnumeric data type that can be implicitly converted to a numeric data type, then Oracle Database determines the argument with the highest numeric precedence, implicitly converts the remaining arguments to that data type, and returns that data type.
See Also:

Table 29 for more information on implicit conversion and Numeric Precedence for information on numeric precedence

Appendix C in Oracle Database Globalization Support Guide for the collation derivation rules, which define the collation assigned to the return value of
COALESCE
when it is a character value
This function is a generalization of the NVL
function.
You can also use COALESCE
as a variety of the CASE
expression. For example,
COALESCE(expr1, expr2)
is equivalent to:
CASE WHEN expr1 IS NOT NULL THEN expr1 ELSE expr2 END
Similarly,
COALESCE(expr1, expr2, ..., exprn)
where n
>= 3, is equivalent to:
CASE WHEN expr1 IS NOT NULL THEN expr1
ELSE COALESCE (expr2, ..., exprn) END
See Also:
NVL and CASE Expressions
Examples
The following example uses the sample oe.product_information
table to organize a clearance sale of products. It gives a 10% discount to all products with a list price. If there is no list price, then the sale price is the minimum price. If there is no minimum price, then the sale price is "5":
SELECT product_id, list_price, min_price, COALESCE(0.9*list_price, min_price, 5) "Sale" FROM product_information WHERE supplier_id = 102050 ORDER BY product_id; PRODUCT_ID LIST_PRICE MIN_PRICE Sale     1769 48 43.2 1770 73 73 2378 305 247 274.5 2382 850 731 765 3355 5