1. Dec 11, 2003Murali Mani SQL with other Programming Languages B term 2004: lecture 16

2. Dec 11, 2003Murali Mani Why? SQL is not for general purpose programming. Eg: Suppose we have a table R (a, factorialA), we want to populate the table as follows: The user inputs a, the program should compute the factorial of a and insert these 2 attributes as 1 row in R. We need to integrate SQL code with general purpose PL code such as COBOL, Fortran, C

3. Dec 11, 2003Murali Mani Architecture Host Language + Embedded SQL Host Language + Function Calls Preprocessor Host Language compiler Executable

4. Dec 11, 2003Murali Mani Oracle with C – Embedded SQL Preprocessor = proc Available at $ORACLE_HOME/bin SET your library path as setenv LD_LIBRARY_PATH ${LD_LIBRARY_PATH}:${ORACLE_HOME}/lib We will create files with extension.pc, example: test.pc We will make them as make -f $ORACLE_HOME/precomp/demo/proc/demo_pro c.mk build EXE=test OBJS=test.o

5. Dec 11, 2003Murali Mani To find about SQL states Use the special variable called SQLSTATE Also there are macros such as SQLERROR, SQLWARNING, NOT FOUND

6. Dec 11, 2003Murali Mani Handling NULL values Using indicator variables Indicator variables need 2 bytes – so typically you set it as short. It is used as EXEC SQL FETCH myCursor INTO :pnumber:isNullNumber, :pname; If isNullNumber has value -1, then that means :pnumber is null

7. Dec 11, 2003Murali Mani Scrollable cursors We may need cursors that can go to any position in the result set, go back, go over the result set multiple times etc. Define a scrollable cursor as EXEC SQL DECLARE myCursor SCROLL CURSOR FOR select sNumber, sName from student; We fetch from scrollable cursor as EXEC SQL FETCH RELATIVE 2 myCursor INTO :snumber:isNullNumber, :sname;

8. Dec 11, 2003Murali Mani Scrollable cursors We can use the following to move the cursor “pointer” around NEXT to give next tuple PRIOR to give previous tuple FIRST to give first tuple in result set LAST to give last tuple in result set RELATIVE where is any positive or negative integer. RELATIVE 1 = NEXT, RELATIVE -1 = PRIOR ABSOLUTE, if num is positive, we count from first, otherwise we count from last. ABSOLUTE 1 = FIRST, ABSOLUTE -1 = LAST

9. Dec 11, 2003Murali Mani Call Level Interface (CLI) Embedded SQL – You write a code specific to your DBMS vendor. CLI – more portable. The code you write is irrespective of the DBMS vendor. Embedded SQL – SQL embedded in C, FORTRAN, PASCAL, COBOL, Java (SQLJ) etc CLI – ODBC (Open Database Connectivity), JDBC (Java Database Connectivity)

10. Dec 11, 2003Murali Mani Architecture for CLI Host Language Host Language compiler Executable

11. Dec 11, 2003Murali Mani CLI with C #include sqlcli.h SQLHENV myEnv; SQLHDBC myCon; SQLHSTMT myStmt; SQLRETURN errorCode; errorCode = SQLAllocHandle (SQL_HANDLE_ENV, SQL_NULL_HANDLE, &myEnv); errorCode = SQLAllocHandle (SQL_HANDLE_DBC, myEnv, &myCon); errorCode = SQLAllocHandle (SQL_HANDLE_STMT, myCon, &myStmt);

12. Dec 11, 2003Murali Mani Executing Statements SQLPrepare (myStmt, “SELECT * from r”, SQL_NTS); SQLExecute (myStmt); (or) SQLExecDirect (myStmt, “SELECT * from r”, SQL_NTS);

13. Dec 11, 2003Murali Mani Fetching tuples (similar to fetching tuples from cursor) SQLFetch (myStmt); To bind values from result to programming language variables. SQLINTEGER a1, a1Info; SQLExecDirect (myStmt, “Select * from r”, SQL_NTS); SQLBindCol (myStmt, 1, SQL_INTEGER, &a1, sizeof (a1), &a1Info);

14. Dec 11, 2003Murali Mani Passing Parameters to SQL queries SQLPrepare (myStmt, “INSERT INTO Student (sNumber, sName) VALUES (?, ?)”, SQL_NTS); SQLBindParameter (myStmt, 1, …, num, …); SQLBindParameter (myStmt, 2, …, name, …); SQLExecute (myStmt);

15. Dec 11, 2003Murali Mani JDBC passing parameters to queries PreparedStatement myStmt = myCon.prepareStatement (“INSERT INTO Student (sNumber, sName) VALUES (?, ?)”); myStmt.setInt (1, num); myStmt.setString (2, name); (or) String query = “INSERT INTO Student (sNumber, sName) VALUES (“ + num + “, ‘” + name + “’)”;