<query>
Stores a set of MDB query operations and performs the calculations when results are required for use.
Description
<query> may be indexed to return a scalar either as
@foo.column.row or
@foo.row.column; it may be partially indexed to return a
package with @foo.row or a list with @foo.column;
@foo._rows returns the number of rows and @foo._cols
returns a list of column names; and @foo._column.column returns a
package of metadata for the specified column.
Rather than storing a full copy of a table's data in memory, it stores the MDB ops for the
query yielding that table. @foo._xml yields the code corresponding to these
ops as an XML value.
Syntax
<query name="variable"> [1010data_QUERY] </query>
Attributes
- name
- Defines the name of the query, which can then be referenced elsewhere in the code.
Example
Store a basic set of MDB query operations in a query object, then index into that object to illustrate the calculation and retrieval of values.
<block> <query name="queryvalue"> <base table="pub.demo.retail.item"/> <sel value="transid=532"/> </query> <willbe name="query_test" value="{@queryvalue.transid}"/> </block>
Example
Show the original MDB query operations stored in this query object
<block>
<query name="queryvalue">
<base table="pub.demo.retail.item"/>
<sel value="transid=532"/>
</query>
<willbe name="query_test" value="'{@queryvalue._xml}'"/>
</block>
Example
Populate a new <table> object with a column from this stored query. The query is not executed until it is necessary to return the values for transid.
<block>
<query name="queryvalue">
<base table="pub.demo.retail.item"/>
<sel value="transid=532"/>
</query>
<table />
<willbe name="foo" value="{@queryvalue.transid}"/>
</block>