List Structures
InterSystems IRIS supports the list structure data type %List (data type class %Library.List). This is a compressed binary format, which does not map to a corresponding native data type for InterSystems SQL. In its internal representation it corresponds to data type VARBINARY with a default MAXLEN of 32749. InterSystems IRIS supports the list structure data type %ListOfBinary (data type class %Library.ListOfBinary) corresponds to data type VARBINARY with a default MAXLEN of 4096.
For this reason, Dynamic SQL cannot use %List data in a WHERE clause comparison. You also cannot use INSERT or UPDATE to set a property value of type %List.
Dynamic SQL returns the data type of list structured data as VARCHAR. To determine if a field in a query is of data type %List or %ListOfBinary you can use the select-item columns metadata isList boolean flag. The CType (client data type) integer code for these data types is 6.
If you use an ODBC or JDBC client, %List data is projected to VARCHAR string data, using LogicalToOdbc conversion. A list is projected as a string with its elements delimited by commas. Data of this type can be used in a WHERE clause, and in INSERT and UPDATE statements. Note that, by default, InterSystems IRIS establishes a system-wide ODBC VARCHAR maximum length of 4096; this ODBC maximum length is configurable.
Also see %Library.ListOpens in a new tab for information on that class. For further details on using lists in a WHERE clause, see the %INLIST predicate and the FOR SOME %ELEMENT predicate. For further details on handling list data as a string, see the %EXTERNAL function.
InterSystems SQL supports eight list functions: $LIST, $LISTBUILD, $LISTDATA, $LISTFIND, $LISTFROMSTRING, $LISTGET, $LISTLENGTH, and $LISTTOSTRING. ObjectScript supports three additional list functions: $LISTVALID to determine if an expression is a list, $LISTSAME to compare two lists, and $LISTNEXT to sequentially retrieve elements from a list.
