Difference between revisions of "KEYLOOKUP()"
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==Syntax== | ==Syntax== | ||
| − | KEYLOOKUP(<workarea | + | KEYLOOKUP(<workarea | alias | table>, <"indextagname">, <keyExpr>, <resultExpr> [, <notfoundExpr>]) |
==See Also== | ==See Also== | ||
| − | + | [[LOOKUP()]], [[RLOOKUP()]], [[SEEK()]], [[SET RELATION]], [[SQLLOOKUP()]] | |
==Description== | ==Description== | ||
| Line 13: | Line 13: | ||
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 | + | 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. | ||
| Line 23: | Line 23: | ||
It can also be used to lookup NoSQL key/value pairs. | 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()]]. | Note: for Virtual Tables, see [[SQLLOOKUP()]]. | ||
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use orders in 0 | use orders in 0 | ||
? keylookup("employees","employeeid",orders.employeeid, lastname, "not found") | ? keylookup("employees","employeeid",orders.employeeid, lastname, "not found") | ||
| − | |||
| − | |||
| − | |||
| − | |||
| − | |||
</code> | </code> | ||
Revision as of 11:47, 10 July 2019
Contents
Purpose
Function to perform a cross-table lookup
Syntax
KEYLOOKUP(<workarea | alias | table>, <"indextagname">, <keyExpr>, <resultExpr> [, <notfoundExpr>])
See Also
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.
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")
