Convert Macro Function (FireDAC)

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The following table presents the CONVERT macro function:

Function	Description	Local expression engine
CONVERT(value_exp, data_type)	The function returns the value specified by value_exp converted to the specified data_type, where data_type is one of the following keywords.	+

The supported keywords:

BIGINT	REAL
BINARY	SMALLINT
BIT	DATE
CHAR	TIME
DECIMAL	TIMESTAMP
TIMESTAMP	TIMESTAMP
FLOAT	VARBINARY
GUID	VARCHAR
INTEGER	WCHAR
LONGVARBINARY	WLONGVARCHAR
LONGVARCHAR	WVARCHAR
NUMERIC

The syntax for the explicit data type conversion function does not support specification of conversion format. The argument value_exp can be a column name, the result of another scalar function, or a numeric or string literal. For example:

{ fn CONVERT( { fn CURDATE() }, CHAR ) }

converts the output of the CURDATE scalar function to a character string. Because FireDAC does not mandate a data type for return values from scalar functions (because the functions are often data source–specific), applications should use the CONVERT scalar function whenever possible to force data type conversion. The following two examples illustrate the use of the CONVERT function. These examples assume the existence of a table called EMPLOYEES, with an EMPNO column of type SQL_SMALLINT and an EMPNAME column of type SQL_CHAR. If an application specifies the following SQL statement:

SELECT EMPNO FROM EMPLOYEES WHERE {fn CONVERT(EMPNO,CHAR)} LIKE '1%'

• A driver for ORACLE translates the SQL statement to:

SELECT EMPNO FROM EMPLOYEES WHERE to_char(EMPNO) LIKE '1%'

• A driver for SQL Server translates the SQL statement to:

SELECT EMPNO FROM EMPLOYEES WHERE convert(char,EMPNO) LIKE '1%'

If an application specifies the following SQL statement:

SELECT {fn ABS(EMPNO)}, {fn CONVERT(EMPNAME,SMALLINT)} FROM EMPLOYEES WHERE EMPNO <> 0

A driver for ORACLE translates the SQL statement to:

SELECT abs(EMPNO), to_number(EMPNAME) FROM EMPLOYEES WHERE EMPNO <> 0

A driver for SQL Server translates the SQL statement to:

SELECT abs(EMPNO), convert(smallint, EMPNAME) FROM EMPLOYEES WHERE EMPNO <> 0