The name of the function to be created in a stored procedure class. The name must be a valid identifier and must be followed by parentheses, even if no parameters are specified. 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()Opens in a new tab method to determine the current system-wide default schema name. The initial system-wide default schema name is SQLUser, which corresponds to the class package name User.
Note that the FOR characteristic (described below) overrides the class name specified in name. If a function 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, “func”, and then 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.
An optional list of parameters used to pass values to the function. The parameter list is enclosed in parentheses, which are mandatory even when no parameters are specified, 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')
-- SQL program code
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.
A function is “correlated” if it takes at least one parameter that is dependent on a value from a row of data, for example the %ID field. Correlated functions are evaluated per row; uncorrelated functions (that is, functions that either take no parameters or take arguments that remain consistent across all rows) are evaluated a single time.
An optional argument that consists of one or more keywords specifying the characteristics of the function. Multiple characteristics are separated by whitespace (a space or line break), and characteristics can be specified in any order. The available keywords are as follows:
||Specifies the name of the class in which to create the function. If the class does not exist, it will be created. You can also specify a class name by qualifying the function name. The class name specified in the FOR clause overrides a class name specified by qualifying the function name.
||Specifies that subclasses cannot override the function. By default, functions are not final. The FINAL keyword is inherited by subclasses.
||Specifies that the function can only be invoked by other function of its own class or subclasses. By default, a function is public, and can be invoked without restriction. This restriction is inherited by subclasses.
||Specifies that the function is projected as an SQL stored procedure. Stored procedures are inherited by subclasses. Because CREATE FUNCTION always projects an SQL stored procedure, this keyword is optional. This keyword can be abbreviated as PROC.
||Specifies the data type of the value returned by a call to the function. If RETURNS is omitted, the function cannot return a value. This specification is inherited by subclasses, and can be modified by subclasses. This datatype can specify type parameters such as MINVAL, MAXVAL, and SCALE. For example RETURNS DECIMAL(19,4). Note that when returning a value, InterSystems IRIS ignores the length of datatype; for example, RETURNS VARCHAR(32) can receive a string of any length that is returned by a call to the function.
||Only used when LANGUAGE is SQL (the default). When specified, InterSystems IRIS adds an #SQLCOMPILE SELECT=mode statement to the corresponding class method, thus generating the SQL statements defined in the method with the specified SELECTMODE. The possible mode values are LOGICAL, ODBC, RUNTIME, and DISPLAY. The default is LOGICAL.
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.StatementOpens in a new tab class %SelectModeOpens in a new tab 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.
The program code for the method to be created. You specify this code in either SQL or ObjectScript. SQL program code is prefaced with a BEGIN keyword and concludes with an END keyword. Each complete SQL statement within code_body end with a semicolon (;). ObjectScript program code is enclosed in curly braces, and code lines must be indented. 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:
&sql( SELECT col FROM tbl )
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.SQLProcContextOpens in a new tab 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:
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. To avoid this error, use the optional OR REPLACE keyword, or drop the old function first with DROP FUNCTION.