CREATE FUNCTION (SQL)

name

The name of the function (method) to be created. This name may be unqualified (StoreName) and take the default schema name, or qualified by specifying the schema name (Patient.StoreName). You can use the $SYSTEM.SQL.Schema.Default() method to determine the current system-wide default schema name. The initial system-wide default schema name is SQLUser corresponds to the class package name User.

Note that the FOR characteristic (described below) overrides the class name specified in name. If a method with this name already exists, the operation fails with an SQLCODE -361 error.

The name of the generated class is the package name corresponding to the schema name, followed by a dot, followed by “func”, followed by the specified name. For example, if the unqualified function name RandomLetter takes the initial default schema SQLUser, the resulting class name would be: User.funcRandomLetter. For further details, see SQL to Class Name Transformations in the “Defining and Using Stored Procedures” chapter of Using InterSystems SQL.

InterSystems SQL does not allow you to specify a duplicate function name that differs only in letter case. Specifying a function name that differs only in letter case from an existing function name results in an SQLCODE -400 error.

parameter-list

A list of parameters used to pass values to the function. The parameter list is enclosed in parentheses, and parameter declarations in the list are separated by commas. Each parameter declaration in the list consists of (in order):

• An optional keyword specifying whether the parameter mode is IN (input value), OUT (output value), or INOUT (modify value). If omitted, the default parameter mode is IN.

• The parameter name. Parameter names are case-sensitive.

• The data type of the parameter.

• Optional: A default value for the parameter. You can specify the DEFAULT keyword followed by a default value; the DEFAULT keyword is optional. If no default is specified, the assumed default is NULL.

The following example specifies two input parameters, both of which have default values. The optional DEFAULT keyword is specified for the first parameter, omitted for the second parameter:

CREATE FUNCTION RandomLetter(IN firstlet CHAR DEFAULT 'A',IN lastlet CHAR 'Z')
BEGIN
-- SQL program code
END

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User-defined functions are supplied to the clauses of a user-defined aggregate function. When defining a function for use in a user-defined aggregate function, you define a state parameter which is used to aggregate and pass the output value.

characteristics

The available keywords are as follows:

The SELECTMODE clause is used for SELECT query operations and for INSERT and UPDATE operations. It specifies the compile-time select mode. The value that you specify for SELECTMODE is added at the beginning of the ObjectScript class method code as: #SQLCompile Select=mode. For further details, see #SQLCompile Select in the “ObjectScript Macros and the Macro Preprocessor” chapter of Using ObjectScript.

• In a SELECT query, the SELECTMODE specifies the mode in which data is returned. If the mode value is LOGICAL, then logical (internal storage) values are returned. For example, dates are returned in $HOROLOG format. If the mode value is ODBC, logical-to-ODBC conversion is applied, and ODBC format values are returned. If the mode value is DISPLAY, logical-to-display conversion is applied, and display format values are returned. If the mode value is RUNTIME, the display mode can be set (to LOGICAL, ODBC, or DISPLAY) at execution time.

• In an INSERT or UPDATE operation, the SELECTMODE RUNTIME option supports automatic conversion of input data values from a display format (DISPLAY or ODBC) to logical storage format. This compiled display-to-logical data conversion code is applied only if the select mode setting when the SQL code is executed is LOGICAL (which is the default for all InterSystems SQL execution interfaces).

When the SQL code is executed, the %SQL.Statement class %SelectMode property specifies the execution-time select mode, as described in “Using Dynamic SQL” chapter of Using InterSystems SQL. For further details on SelectMode options, refer to “Data Display Options” in the “InterSystems IRIS SQL Basics” chapter of Using InterSystems SQL.

LANGUAGE

A keyword clause specifying the procedure code language. Available options are:

• LANGUAGE OBJECTSCRIPT (for ObjectScript) or LANGUAGE SQL. The procedure code is specified in the code_body.

• LANGUAGE JAVA, LANGUAGE PYTHON, or LANGUAGE DOTNET for an SQL procedure that invokes an external stored procedure in one of these languages. The syntax for an external stored procedure is as follows:

  LANGUAGE langname EXTERNAL NAME external-routine-name

  Where langname is JAVA, PYTHON, or DOTNET and external-routine-name is a quoted string containing the name an external routine in the specified language. The SQL procedure invokes an existing routine; you cannot write code in these languages within the CREATE FUNCTION statement. Stored procedure libraries in these languages are stored external to IRIS, and therefore do not have to be packaged, imported, or compiled within IRIS. The following is an example of a CREATE FUNCTION that invokes an existing JAVA external stored procedure that returns a value:

  CREATE FUNCTION getPrice (item_name VARCHAR)
  RETURNS INTEGER
  LANGUAGE JAVA  
  EXTERNAL NAME 'Orders.getPrice'

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If the LANGUAGE clause is omitted, SQL is the default.

code_body

The program code for the method to be created. You specify this code in either SQL or ObjectScript. The language used must match the LANGUAGE clause. However, code specified in ObjectScript can contain embedded SQL.

InterSystems IRIS uses the code you supply to generate the actual code of the method. If the code you specify is SQL, InterSystems IRIS provides additional lines of code when generating the method that embed the SQL in an ObjectScript “wrapper,” provide a procedure context handler (if necessary), and handle return values. The following is an example of this InterSystems IRIS-generated wrapper code:

   NEW SQLCODE,%ROWID,%ROWCOUNT,title
   &sql( SELECT col FROM tbl )
   QUIT $GET(title)

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If the code you specify is OBJECTSCRIPT, the ObjectScript code must be enclosed in curly braces. All code lines must be indented from column 1, except for labels and macro preprocessor directives. A label or macro directive must be prefaced by a colon (:) in column 1.

For ObjectScript code, you must explicitly define the “wrapper” (which NEWs variables, and uses QUIT to exit and (optionally) to return a value upon completion).

When a stored procedure is called, an object of the class %Library.SQLProcContext is instantiated in the %sqlcontext variable. This procedure context handler is used to pass the procedure context back and forth between the procedure and its caller (for example, the ODBC server).

%sqlcontext consists of several properties, including an Error object, the SQLCODE error status, the SQL row count, and an error message. The following example shows the values used to set several of these:

  SET %sqlcontext.%SQLCODE=SQLCODE
  SET %sqlcontext.%ROWCOUNT=%ROWCOUNT
  SET %sqlcontext.%Message=%msg

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The values of SQLCODE and %ROWCOUNT are automatically set by the execution of an SQL statement. The %sqlcontext object is reset before each execution.

Alternatively, an error context can be established by instantiating a %SYSTEM.Error object and setting it as %sqlcontext.Error.

An SQLCODE -361 error is generated if the specified function already exists.