Syntax
Purpose
COALESCE
returns the first non-null 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 short-circuit 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 2-8 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