Rules for result data types

The data types of a result are determined by rules which are applied to the operands in an operation. This section explains those rules.

These rules apply to:

Corresponding columns in UNION, UNION ALL, EXCEPT, or INTERSECT operations
Result expressions of a CASE expression
Arguments of the scalar functions COALESCE, IFNULL, MAX, MIN, and VALUE
Expression values of the IN list of an IN predicate

For the result data type of expressions that involve the operators /, *, + and -, see Expressions. For the result data type of expressions that involve the CONCAT operator, see With the concatenation operator.

The data type of the result is determined by the data type of the operands. The data types of the first two operands determine an intermediate result data type, this data type and the data type of the next operand determine a new intermediate result data type, and so on. The last intermediate result data type and the data type of the last operand determine the data type of the result. For each pair of data types, the result data type is determined by the sequential application of the rules summarized in the tables that follow.

If neither operand column allows nulls, the result does not allow nulls. Otherwise, the result allows nulls.

If the data type and attributes of any operand column are not the same as those of the result, the operand column values are converted to conform to the data type and attributes of the result. The conversion operation is exactly the same as if the values were assigned to the result. For example,

If one operand column is CHAR(10), and the other operand column is CHAR(5), the result is CHAR(10), and the values derived from the CHAR(5) column are padded on the right with five blanks.
If the whole part of a number cannot be preserved then an error is returned.

Numeric operands

Numeric types are compatible with other numeric and character-string and graphic-string data types.

If one operand column is...	And the other operand is...	The data type of the result column is...
SMALLINT	SMALLINT	SMALLINT
SMALLINT	String	INTEGER
INTEGER	SMALLINT	INTEGER
INTEGER	INTEGER	INTEGER
INTEGER	String	INTEGER
BIGINT	SMALLINT	BIGINT
BIGINT	INTEGER	BIGINT
BIGINT	BIGINT	BIGINT
BIGINT	String	BIGINT
DECIMAL(w,x)	SMALLINT	DECIMAL(p,x) where p = min(mp, x+max(w-x,5)) mp = 31 or 63 (See Note 1)
DECIMAL(w,x)	INTEGER	DECIMAL(p,x) where p = min(mp, x+max(w-x,11)) mp = 31 or 63 (See Note 1)
DECIMAL(w,x)	BIGINT	DECIMAL(p,x) where p = min(mp, x+max(w-x,19)) mp = 31 or 63 (See Note 1)
DECIMAL(w,x)	DECIMAL(y,z) or NUMERIC(y,z,)	DECIMAL(p,s) where p = min(mp, max(x,z)+max(w-x,y-z)) s = max(x,z) mp = 31 or 63 (See Note 1)
DECIMAL(w,x)	String	DECIMAL(w,x)
NUMERIC(w,x)	SMALLINT	NUMERIC(p,x) where p = min(mp, x + max(w-x,5)) mp = 31 or 63 (See Note 1)
NUMERIC(w,x)	INTEGER	NUMERIC(p,x) where p = min(mp, x + max(w-x,11)) mp = 31 or 63 (See Note 1)
NUMERIC(w,x)	BIGINT	NUMERIC(p,x) where p = min(mp, x + max(w-x,19)) mp = 31 or 63 (See Note 1)
NUMERIC(w,x)	NUMERIC(y,z)	NUMERIC(p,s) where p = min(mp, max(x,z) + max(w-x, y-z)) s = max(x,z) mp = 31 or 63 (See Note 1)
NUMERIC(w,x)	String	NUMERIC(w,x)
NONZERO SCALE BINARY	NONZERO SCALE BINARY	NONZERO SCALE BINARY (If either operand is nonzero scale binary, both operands must be binary with the same scale.)
REAL	REAL	REAL
REAL	DECIMAL, NUMERIC, BIGINT, INTEGER, or SMALLINT	DOUBLE
REAL	String	DOUBLE
DOUBLE	any numeric type	DOUBLE
DOUBLE	String	DOUBLE
Notes: The value of mp is 63 if: either w or y is greater than 31, or a value of 63 was specified for the maximum precision on the DECRESULT parameter of the CRTSQLxxx command, RUNSQLSTM command, or SET OPTION statement Otherwise, the value of mp is 31.

Character and graphic string operands

Character and graphic strings are compatible with other character and graphic strings when there is a defined conversion between their corresponding CCSIDs.

If one operand column is...	And the other operand is...	The data type of the result column is...
CHAR(x)	CHAR(y)	CHAR(z) where z = max(x,y)
GRAPHIC(x)	GRAPHIC(y) or CHAR(y)	GRAPHIC(z) where z = max(x,y)
VARCHAR(x)	VARCHAR(y) or CHAR(y)	VARCHAR(z) where z = max(x,y)
VARCHAR(x)	GRAPHIC(y)	VARGRAPHIC(z) where z = max(x,y)
VARGRAPHIC(x)	VARGRAPHIC(y) or GRAPHIC(y) or VARCHAR(y) or CHAR(y)	VARGRAPHIC(z) where z = max(x,y)
CLOB(x)	CLOB(y) or VARCHAR(y) or CHAR(y)	CLOB(z) where z = max(x,y)
CLOB(x)	GRAPHIC(y) or VARGRAPHIC(y)	DBCLOB(z) where z = max(x,y)
DBCLOB(x)	CHAR(y) or VARCHAR(y) or CLOB(y) or GRAPHIC(y) or VARGRAPHIC(y) or DBCLOB(y)	DBCLOB(z) where z = max(x,y)

The CCSID of the result graphic string will be derived based on the Conversion rules for operations that combine strings.

Binary string operands

Binary strings are compatible only with other binary strings. Other data types can be treated as a binary-string data type by using the BINARY, VARBINARY, or BLOB scalar functions to cast the data type to a binary string.

If one operand column is...	And the other operand is...	The data type of the result column is...
BINARY(x)	BINARY(y)	BINARY(z) where z = max(x,y)
VARBINARY(x)	VARBINARY(y) or BINARY(y)	VARBINARY(z) where z = max(x,y)
BLOB(x)	BLOB(y) or VARBINARY(y) or BINARY(y)	BLOB(z) where z = max(x,y)

Datetime operands

A DATE type is compatible with another DATE type or any character string expression that contains a valid string representation of a date. A string representation must not be a CLOB. The data type of the result is DATE.

A TIME type is compatible with another TIME type or any character string expression that contains a valid string representation of a time. A string representation must not be a CLOB. The data type of the result is TIME.

A TIMESTAMP type is compatible with another TIMESTAMP type or any character string expression that contains a valid string representation of a timestamp. A string representation must not be a CLOB. The data type of the result is TIMESTAMP.

If one operand column is...	And the other operand is...	The data type of the result column is...
DATE	DATE, CHAR(y), or VARCHAR(y)	DATE
TIME	TIME, CHAR(y), or VARCHAR(y)	TIME
TIMESTAMP	TIMESTAMP, CHAR(y), or VARCHAR(y)	TIMESTAMP

DataLink operands

A DataLink is compatible with another DataLink. However, DataLinks with NO LINK CONTROL are only compatible with other DataLinks with NO LINK CONTROL; DataLinks with FILE LINK CONTROL READ PERMISSION FS are only compatible with other DataLinks with FILE LINK CONTROL READ PERMISSION FS; and DataLinks with FILE LINK CONTROL READ PERMISSION DB are only compatible with other DataLinks with FILE LINK CONTROL READ PERMISSION DB. The data type of the result is DATALINK. The length of the result DATALINK is the largest length of all the data types.

If one operand column is...	And the other operand is...	The data type of the result column is...
DATALINK(x)	DATALINK(y)	DATALINK(z) where z = max(x,y)

ROWID operands

A ROWID is compatible with another ROWID. The data type of the result is ROWID.

Distinct type operands

A user-defined distinct type is compatible only with the same user-defined distinct type. The data type of the result is the user-defined distinct type.

If one operand column is...	And the other operand is...	The data type of the result column is...
Distinct Type	Distinct Type	Distinct Type

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