Tdbc_Init

Section: Tcl Database Connectivity (3)
Updated: 8.6
Page Index

NAME

Tdbc_Init, Tdbc_MapSqlState, Tdbc_TokenizeSql - C procedures to facilitate writing TDBC drivers

SYNOPSIS

#include <tdbc.h>

int
Tdbc_Init(interp)

Tcl_Obj *
Tdbc_TokenizeSql(interp, sqlcode)

const char *
Tdbc_MapSqlState(state)

ARGUMENTS

Tcl_Interp *interp (in/out) Pointer to a Tcl interpreter.

const char *state (in) Pointer to a character string containing a 'SQL state' from a database error.

const char *sqlcode (in) Pointer to a character string containing a SQL statement.

DESCRIPTION

The TDBC library provides several C procedures that simplify writing a TDBC driver. They include a procedure that tokenizes a SQL statement, locating variables to be substituted, and a procedure that accepts a SQL state and returns an error class for the interpreter error information.

Tdbc_Init must be invoked prior to any other TDBC call. It accepts a pointer to a Tcl interpreter, and arranges to load the TDBC library. It returns TCL_OK if the Tcl library was loaded successfully, and TCL_ERROR otherwise. If TCL_ERROR is returned, the interpreter's result contains the error message.

Tdbc_TokenizeSql accepts a pointer to a Tcl interpreter, and a pointer to a character string containing one or more SQL statements. It tokenizes the SQL statements, and returns a pointer to a Tcl_Obj that contains a list of the tokens that make up the statement. Concatenating the tokens together will yield the original SQL code. The returned Tcl_Obj has a reference count of zero. The caller is responsible for managing the reference count as needed. See TOKENS below for a description of what may be in the returned list of tokens.

Tdbc_MapSqlState accepts a pointer to a string, usually five characters long, that is the 'SQL state' that resulted from a database error. It returns a character string that is suitable for inclusion as the error class when constructing the error code for an error in a TDBC driver. (By convention, the error code is a list having at least four elements: "TDBC errorClass sqlstate driverName details...".)

TOKENS

Each token returned from Tdbc_TokenizeSql may be one of the following:

[1]: A bound variable, which begins with one of the characters ':', '@', or '$'. The remainder of the string is the variable name and will consist of alphanumeric characters and underscores. (The leading character will be be non-numeric.)
[2]: A semicolon that separates two SQL statements.
[3]: Something else in a SQL statement. The tokenizer does not attempt to parse SQL; it merely identifies bound variables (distinguishing them from similar strings appearing inside quotes or comments) and statement delimiters.

KEYWORDS

TDBC, SQL, database, tokenize