The ProGrammar ActiveX control makes it easy to parse SQL statements from Visual Basic, Visual C++, Delphi, and other Windows-based applications.

The following example shows how to parse SQL from a Visual Basic program. While this example is intentionally very simple, it demonstrates the main steps involved in using ProGrammar in your applications.

The first step is to initialize the ProGrammar ActiveX control:

' Create an interface to the parser Dim parser As Pgmr Set parser = new Pgmr

The next step is loading the SQL grammar. The grammar is stored as a binary file named "SQL.GMR", which was generated by the ProGrammar IDE when the
SQL grammar definition was compiled.

' Load the SQL grammar parser.SetGrammar ("SQL.GMR")

The following SQL grammars are currently available:

SQL	A simple subset of the SQL language
SQL92	The full SQL92 grammar, based on ISO standard SQL2
TSQL	A Beta version of the TSQL grammar

Next, the program sets the SQL text that will be parsed. The parser can load the text from a file or parse it directly from a memory buffer. In this example, the SQL text is contained in a file named "myfile.sql".

' Load the SQL file that will be parsed parser.SetInputFilename ("myfile.sql")

The program then parses the file and checks for parse errors.

' Parse the SQL file parser.Parse ' Show parse errors (if any) numErrors = parser.GetNumErrors For errorIndex = 0 To numErrors    errorCode = parser.GetErrorCode(errorIndex)    desc = parser.GetErrorDescription(errorIndex)    ' TODO: display error to the user Next errorIndex

When the Parse method is called, ProGrammar parses the input text using the SQL grammar and builds a parse tree data structure in memory. The program then calls ActiveX methods to retrieve relevant data items from the parse tree.

In this example, the program creates a list of all tables that are referenced by name in the SQL statements. In the SQL grammar definition, a table name is represented by a symbol named "table". Therefore, each reference to a table in the input text will have a corresponding node in the parse tree labeled "table", whose value is the name of the table.

If parser.Status = pgStatusComplete Then    ' Search the tree for all 'table' nodes    searchID = parser.StartSearch ("/.*table", 0)    Do       ' Find the next node matching the search pattern       tableNodeID = parser.FindNext (searchID)       If tableNodeID <> 0 Then          ' get the value of this node          tableName = parser.GetValue (tableNodeID)          ' TODO: Now, do something with the table name       End If    Loop Until tableNodeID = 0    parser.EndSearch (searchID) End If