Use InstallShield 12 to check whether ms SQL Server or MSDE is installed

I have been searching for this stuff on the Internet for a long time, either incomplete or not what I wanted. I finally figured it out and posted it. Please help me to see if there are still defects.

// Global variable
String szsqlservicename; // database server name
String szsqlservicename1; // database server name (cache)
String szsqlservicefilepath; // path of the execution file of the Database Server
String szsqlservicedatarootpath; // Database Server database root path
String szsqlservicefilerootpath; // root path of the Database Server File
String szstartserviceargs; // sum of startup parameters
String szsqlservicerundata0; // database server startup parameter 1
String szsqlservicerundata1; // database server startup parameter 2
String szsqlservicerundata2; // database server startup parameter 3
Number szservicestate; // Database Service startup status

// Check when installation starts
Function onbegin ()
String szmsg;
String skey, skeyarg, svalue, sdata;
String szkey;
Number ntype, nsize;
Number nresult;
String szwaittxt;
Begin

If! Maintenance then
Sdshowmsg ("checking the software runtime environment... please wait", true );
Delay (1 );
// Determine whether Microsoft SQL Server or MSDE is installed.
Skey = "software // Microsoft SQL Server ";
Szmsg = "micorsoft SQL Server or MSDE is not installed. Please install micorsoft SQL Server or MSDE first .";

Regdbsetdefaultroot (HKEY_LOCAL_MACHINE );
Nresult = regdbgetkeyvalueex (skey, "installedinstances", ntype, sdata, nsize );
If (nresult <0) then
Sdshowmsg ("msde2000 is being installed. Please wait...", true );
Delay (1 );
If (launchappandwait ("MSDE // setup.exe", "", laaw_option_wait | laaw_option_maximized) <0) then
Sdshowmsg ("", false );
MessageBox ("msde2000installation failed. Please manually install the msde2000 engine in setup.exe under the optical disk msdedirectory./n. If the problem persists, contact the system supplier! ", Severe );
Abort;
Endif;
Endif;
// Obtain the server name
Nresult = regdbgetkeyvalueex (skey, "installedinstances", ntype, szsqlservicename1, nsize );
If (nresult <0) then
// MessageBox ("An error occurred while obtaining the database server name! ", Information );
Szsqlservicename = "MSSQL ";
Else
If (szsqlservicename1 = "") then
Szsqlservicename = "MSSQL ";
Elseif (szsqlservicename1! = "MSSQLServer") then
Szsqlservicename = "MSSQL $" + szsqlservicename1;
Else
Szsqlservicename = szsqlservicename1;
Endif;
Endif;
// Obtain the root path of the database file
If (szsqlservicename1! = "MSSQLServer") then
Skey = "software // Microsoft SQL Server //" + szsqlservicename1 + "// setup ";
Else
Skey = "software // Microsoft //" + szsqlservicename1 + "// MSSQLServer // setup ";
Endif;
Regdbgetkeyvalueex (skey, "sqldataroot", ntype, szsqlservicedatarootpath, nsize); // database root path
Regdbgetkeyvalueex (skey, "sqldataroot", ntype, szsqlservicefilerootpath, nsize); // file root path
// Path of the database Startup File
Szsqlservicefilepath = szsqlservicefilerootpath + "// binn // sqlservr.exe ";
 
// Obtain the database server startup parameters
If (szsqlservicename1! = "MSSQLServer") then
Skeyarg = "software // Microsoft SQL Server //" + szsqlservicename1 + "// MSSQLServer // Parameters ";
Else
Skeyarg = "software // Microsoft //" + szsqlservicename1 + "// MSSQLServer // Parameters ";
Endif;
Regdbgetkeyvalueex (skey, "sqlarg0", ntype, szsqlservicerundata0, nsize );
Regdbgetkeyvalueex (skey, "sqlarg1", ntype, szsqlservicerundata1, nsize );
Regdbgetkeyvalueex (skey, "sqlarg2", ntype, szsqlservicerundata2, nsize );
Szstartserviceargs = "-c" + szsqlservicerundata0 + "" + szsqlservicerundata1 + "" + szsqlservicerundata2;

// Check whether the database service is enabled
If (servicegetservicestate (szsqlservicename, szservicestate) <iserr_success) then
// Load
Serviceaddservice (szsqlservicename, szsqlservicefilepath, true, szstartserviceargs );
Endif;
// Start the Database Service
If (servicestartservice (szsqlservicename, "") <iserr_success) then
Sdshowmsg ("", false );
Setdialogtitle (dlg_msg_information, "Database Service Startup error ");
MessageBox ("Database Service" + szsqlservicename + "Startup error! Manually enable the database service before executing the software installation program. /N. If the problem persists, contact the system supplier! ", Information );
Abort;
Endif;
Endif;
End;