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Rule description

• Unary prefix operators should not be repeated

Non-compliant Code Example

SELECT 
    NAME,
    ADDRESS,
    CREDIT_LIMIT       
FROM
    CUSTOMERS
WHERE NAME NOT IN (SELECT NAME FROM VENDOR WHERE NAME IS NOT NULL);  --Non compliant code (Unary prefix operator repeated)

Compliant Code Example

SELECT 
    NAME,
    ADDRESS,
    CREDIT_LIMIT       
FROM
    CUSTOMERS
INNER JOIN VENDOR
	ON VENDOR.NAME IS NOT NULL AND VENDOR.NAME <> CUSTOMERS.NAME; --Compliant code