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From: =?UTF-8?Q?Arne_Vajh=C3=B8j?= <arne@vajhoej.dk>
Newsgroups: comp.os.vms
Subject: Re: VMS x86-64 database server
Date: Mon, 7 Jul 2025 14:07:31 -0400
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On 7/6/2025 10:42 PM, Lawrence D'Oliveiro wrote:
> On Sun, 6 Jul 2025 19:58:04 -0400, Arne Vajhøj wrote:
>> But in embedded SQL then it is the standard way to do queries.
> 
> Not sure what “embedded SQL” means. I normally use SQL “embedded” in an
> app written in some other programming language.

Embedded SQL is a thing or was a thing 30-40-50 years ago.

Basically you write source code with SQL statements prefixed
by EXEC SQL, put it through a pre-compiler to get valid
code in whatever language (Cobol, PL/I, C or whatever).

Here is C call API code:

     PGresult *res;
     res = PQprepare(con, "stmt_selectf1f2fromt1", "SELECT f1,f2 FROM 
t1", 0, NULL);
     PQclear(res);
     res = PQexecPrepared(con, "stmt_selectf1f2fromt1", 0, NULL, NULL, 
NULL, 0);
     int nrows = PQntuples(res);
     for(int i = 0; i < nrows; i++)
     {
         int f1 = atoi(PQgetvalue(res, i, 0));
         char f2[51];
         strcpy(f2, PQgetvalue(res, i, 1));
         printf("%d %s\n", f1, f2);
     }
     PQclear(res);
     PQexec(con, "DEALLOCATE stmt_selectf1f2fromt1");

same code as C with embedded SQL:

     EXEC SQL DECLARE mycursor CURSOR FOR SELECT f1,f2 FROM t1;
     EXEC SQL OPEN mycursor;
     for(;;)
     {
         EXEC SQL FETCH mycursor INTO :f1, :f2;
         if(sqlca.sqlcode != 0) break;
         printf("%d %s\n", f1, f2);
     }
     EXEC SQL CLOSE mycursor;

Simpler shorter code, because the pre-compiler handle
some of the plumbing.

Arne