The BDB SQL interface comes as a part of the Oracle Berkeley DB download. This can be downloaded from the Oracle Berkeley DB download page.
How you install the BDB SQL interface differs depending on whether you are using a Unix or a Windows system.
                    The BDB SQL interface is automatically built and installed
                    whenever you build or install Berkeley DB for a Windows
                    system. The BDB SQL interface dlls and the
                    command line interpreter have names that differ from a
                    standard SQLite distribution as follows:
                
                            dbsql.exe
                        
This is the command line shell. It operates identically to the SQLite sqlite3.exe shell.
                            libdb_sql50.dll
                        
                            This is the library that provides the BDB SQL interface.
                            It is the equivalent of the SQLite
                            sqlite3.dll library.
                        
                    In order to build the BDB SQL interface, you download and build
                    Berkeley DB, configuring it so that the BDB SQL interface is also built.
                    Be aware that it is not built by default. Instead, you
                    need to tell the Berkeley DB configure
                    script to also build the BDB SQL interface.  For instructions on
                    building the BDB SQL interface, see Building the DB SQL Interface in the
                    Berkeley DB Installation and Build Guide.
                
                    The library and application names used when building
                    the BDB SQL interface are different than those used by SQLite.
                    If you want library and command shell names that are
                    consistent with the names used by SQLite, configure
                    the BDB SQL interface build using the compatibility
                    (--enable-sql_compat) option.
                
The compatibility option can break other applications on your platform that rely on standard SQLite. This is especially true of Mac OS X, which uses standard SQLite for a number of default applications.
Use the compatibility option only if you know exactly what you are doing.
Unless you built the BDB SQL interface with the compatibility option, libraries and a command line shell are built with the following names:
This is the command line shell. It operates identically to the SQLite sqlite3 shell.
                            libdb_sql
                        
                            This is the library that provides the BDB SQL interface.
                            It is the equivalent of the SQLite
                            libsqlite3 library.