SQLCHECKUNIQUE()

Purpose

Function to check whether a prospective column value is unique

Syntax

SQLCHECKUNIQUE(<cTable>, <cKeyField>, <cKeyValue>[, <lAllowblank>])

See Also

KEYLOOKUP(), LOOKUP(), RLOOKUP(), SEEK(), SET RELATION, SQLLOOKUP()

Description

The SQLCHECKUNIQUE() function checks the uniqueness of a prospective column value. The function will auto-detect if the specified table is a native Lianja table or a Virtual Table and act accordingly.

You should always provide a fully qualified database!table if your app is to work in Web/Mobile e.g "southwind!employees".

The logical return value is .T. if the cKeyValue value already exists and .F. if it does not already exist in the cKeyField table column.

Keywords	Description
cTable	Character expression to specify the table to be checked (native or Virtual Table).
cKeyField	Character expression to specify the column in the table to be checked.
cKeyValue	Character expression containing the value to be compared against cKeyField. If this is a character field then enclose it in quotes within quotes: " 'string' ". If it is a numeric then enclose it like this "1".
lAllowblank	Logical expression specifying whether blank values should be ignored.

Example

// Character cKeyField
nCustIDUnique = sqlcheckunique("southwind!customers","customerid","'ALFKI'")
// Numeric cKeyField
nEmpIDUnique = sqlcheckunique("southwind!employees","employeeid","3")
// Ignore blanks
lCustIDUnique = sqlcheckunique("southwind!customers","customerid","''",.t.)
// Include blanks
lCustIDUnique = sqlcheckunique("southwind!customers","customerid","''",.f.)