SQLCHECKUNIQUE()
From Lianjapedia
Contents
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.)