Difference between revisions of "KEYLOOKUP()"
Yvonne.milne (Talk | contribs) (→Description) |
Yvonne.milne (Talk | contribs) (→Description) |
||
Line 11: | Line 11: | ||
The KEYLOOKUP() function looks up the specified index <keyExpr> in the index <indextagname> of the specified <workarea | alias | table>. | 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 <resultExpr> if the <key expression> is found | + | The KEYLOOKUP() function then evaluates the expression <valueExpr>, and returns the value of the <resultExpr> 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 KEYLOOKUP() function returns a null string if the <key expression> is not found or the <notfoundExpr>, if specified. | ||
+ | |||
+ | Note that in JavaScript, the <resultExpr> and <notfoundExpr> must be enclosed in quotes and passed as strings if the expressions contain any field names. | ||
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. |
Revision as of 06:58, 24 February 2020
Contents
Purpose
Function to perform a cross-table lookup
Syntax
KEYLOOKUP(<workarea | alias | table>, <"indextagname">, <keyExpr>, <resultExpr> [, <notfoundExpr>])
See Also
INDEX, LOOKUP(), RLOOKUP(), SEEK(), SET RELATION, SQLLOOKUP()
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 <resultExpr> 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.
Note that in JavaScript, the <resultExpr> and <notfoundExpr> must be enclosed in quotes and passed as strings if the expressions contain any field names.
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.
You should always provide a fully qualified database!table if your app is to work in Web/Mobile e.g "southwind!employees".
If you use this function in Web/Mobile clients you should always specify the resultExpr for keyLookup() as a string prefixed with ? so that the parameter can be proxied correctly back to the server without throwing a JavaScript error on the client. e.g. "?lastname".
Note: for Virtual Tables, see SQLLOOKUP().
Example
open database southwind use orders in 0 ? keylookup("employees","employeeid",orders.employeeid, lastname, "not found")