Difference between revisions of "KEYLOOKUP()"
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==Syntax== | ==Syntax== | ||
| − | KEYLOOKUP(<workarea | alias | table>, <"indextagname">, <keyExpr>, <valueExpr>) | + | KEYLOOKUP(<workarea | alias | table>, <"indextagname">, <keyExpr>, <valueExpr> [, <notfoundExpr>]) |
==See Also== | ==See Also== | ||
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==Description== | ==Description== | ||
| − | The KEYLOOKUP() function looks up the specified index <keyExpr> in the index <indextagname> of the specified <workarea | alias | table>. The KEYLOOKUP() function then evaluates the expression <valueExpr>, and returns the value of the <valueExpr> if the <key expression> is found. The KEYLOOKUP() function returns a null string if the <key expression> is not found. | + | The KEYLOOKUP() function looks up the specified index <keyExpr> in the index <indextagname> of the specified <workarea | alias | table>. The KEYLOOKUP() function then evaluates the expression <valueExpr>, and returns the value of the <valueExpr> if the <key expression> is found. The KEYLOOKUP() function returns a null string if the <key expression> is not found or the <notfoundExpr>, if specified. |
The current record position in the specified <workarea | alias | table> cursor is not moved so this function can also safely be used in SQL queries. | The current record position in the specified <workarea | alias | table> cursor is not moved so this function can also safely be used in SQL queries. | ||
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open database southwind | open database southwind | ||
use orders in 0 | use orders in 0 | ||
| − | ? keylookup("employees","employeeid",orders.employeeid, | + | ? keylookup("employees","employeeid",orders.employeeid, lastname, "not found") |
</code> | </code> | ||
Revision as of 09:47, 30 April 2013
Contents
Purpose
Function to perform a cross-table lookup
Syntax
KEYLOOKUP(<workarea | alias | table>, <"indextagname">, <keyExpr>, <valueExpr> [, <notfoundExpr>])
See Also
LOOKUP(), RLOOKUP(), SEEK(), SET RELATION
Description
The KEYLOOKUP() function looks up the specified index <keyExpr> in the index <indextagname> of the specified <workarea | alias | table>. The KEYLOOKUP() function then evaluates the expression <valueExpr>, and returns the value of the <valueExpr> if the <key expression> is found. The KEYLOOKUP() function returns a null string if the <key expression> is not found or the <notfoundExpr>, if specified.
The current record position in the specified <workarea | alias | table> cursor is not moved so this function can also safely be used in SQL queries.
If the specified table is not already open then Lianja will open the table automatically.
This function can be used to dynamically lookup foreign key values in target tables.
It can also be used to lookup NoSQL key/value pairs.
Example
open database southwind use orders in 0 ? keylookup("employees","employeeid",orders.employeeid, lastname, "not found")
