Article ID: 92359 - View products that this article applies to.
This article was previously published under Q92359
The LOOKUP() function searches a database for the first occurrence of a specified expression. If FoxPro finds the expression, it moves the record pointer to the record that corresponds to the expression and returns the contents of the specified field in the record. If no matching record is found, the function returns the NULL string and leaves the record pointer at the end of the file.
The LOOKUP() function can be used either to search for a specific expression in a database or to search for the first occurrence of a matching field in a second database.
The syntax of the LOOKUP() function is as follows
<field1> is the field to return. <expr> is the string to search for. <field2> is the field to search. <expC> is the compact index tag to use in the search (optional).
The following code searches the CUSTOMER.DBF file for the first occurrence of "Mark Cummings" in the CONTACT field. If LOOKUP() finds a matching record, it returns the contents of the COMPANY field.
USE CUSTOMER ?LOOKUP(COMPANY,"Mark Cummings",CONTACT)
The following code uses both the CUSTOMER.DBF and INVOICES.DBF files. LOOKUP() moves the record pointer through the CUSTOMER database until it finds a record that matches the current CNO field in INVOICES. LOOKUP() returns the contents of the COMPANY field in the CUSTOMER database.
SELECT A USE INVOICES SELECT B USE CUSTOMER ?LOOKUP(COMPANY,INVOICES.CNO,CNO)
If LOOKUP() includes the name of a compact index tag in the optional character expression <expC>, the search expression should match the index expression for the compact index tag. You can search the database for the contents of one field or a combination of fields by including the name of a compact index tag. The following code adds the CONTACT tag to the first example above:
When the LOOKUP() expression does not specify a tag and the database is indexed, FoxPro searches the primary index for the expression. If no index is available, the LOCATE command is used to search the database.
NOTE: The Rushmore query-optimization system cannot optimize a LOOKUP() call.