Therefore, a hash collision is guaranteed for any two strings where the only differences are dashes. With a specified MD5 hash algorithm, the probability that HASHBYTES will return the same result, for two different inputs, is much lower compared to CHECKSUM.ĬHECKSUM ignores the nchar and nvarchar dash character ( N'-' or nchar(45)). Otherwise, consider using HASHBYTES instead. Therefore, to detect whether values have changed, we recommend use of CHECKSUM only if your application can tolerate an occasional missed change. If at least one of the values in the expression list changes, the list checksum will probably change. Null values of a specified type are defined to compare as equal for CHECKSUM function purposes. The CHECKSUM function satisfies hash function properties: CHECKSUM applied over any two lists of expressions will return the same value, if the corresponding elements of the two lists have the same data type, and if those corresponding elements have equality when compared using the equals (=) operator. This can be used for equality searches over the columns. A hash index will result if the CHECKSUM function has column arguments, and an index is built over the computed CHECKSUM value. Use this hash value to build hash indexes. Return typesĬHECKSUM computes a hash value, called the checksum, over its argument list. Noncomparable data types include:Īnother noncomparable data type is sql_variant with any one of the preceding data types as its base type.Īn expression of any type, except a noncomparable data type. CHECKSUM returns an error if any column has a noncomparable data type. This argument specifies that the checksum computation covers all table columns.
This syntax is not supported by serverless SQL pool in Azure Synapse Analytics.
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