SQLJ

SQLJ is an outdated working title for efforts to combine Java and SQL. It consists of the three parts 0, 1 and 2. Part 0 describes the possibility of embedding SQL statements into Java programs. SQLJ part 0 is the basis for part 10 of the SQL:1999 standard, aka SQL Object Language Bindings (SQL/OLB).^[1] SQLJ parts 1 and 2 describes the converse possibility to use Java classes (routines and types) from SQL statements. Parts 1 and 2 are the basis for part 13 of the SQL standard, SQL Routines and Types Using the Java Programming Language (SQL/JRT).

ANSI standards

SQLJ part 0: ANSI X3.135.10-1998
SQLJ part 1: ANSI NCITS 331.1-1999
SQLJ part 2: ANSI NCITS 331.2-2000

SQLJ part 0

In the following SQLJ is a synonym for SQLJ part 0.

Whereas JDBC provides an API, SQLJ consists of a language extension. Thus programs containing SQLJ must be run through a preprocessor (the SQLJ translator) before they can be compiled.

Advantages and disadvantages

Some advantages of SQLJ over JDBC include:

SQLJ commands tend to be shorter than equivalent JDBC programs.
SQL syntax can be checked at compile time. The returned query results can also be checked strictly.
Preprocessor might generate static SQL which performs better than dynamic SQL because query plan is created on program compile time, stored in database and reused at runtime. Static SQL can guarantee worst case reply time and access plan stability. IBM DB2 supports static SQL use in SQLJ programs.

Disadvantages include:

SQLJ requires a preprocessing step.
Many IDEs do not have SQLJ support.
SQLJ lacks support for most of the common persistence frameworks, such as Hibernate.

Examples

The following examples compare SQLJ syntax with JDBC usage.

Multi-row query

JDBC

SQLJ

PreparedStatement stmt = conn.prepareStatement(
   "SELECT LASTNAME"
 + " , FIRSTNME"
 + " , SALARY"
 + " FROM DSN8710.EMP"
 + " WHERE SALARY BETWEEN ? AND ?");
stmt.setBigDecimal(1, min);
stmt.setBigDecimal(2, max);
ResultSet rs = stmt.executeQuery();
while (rs.next()) {
  lastname = rs.getString(1);
  firstname = rs.getString(2);
  salary = rs.getBigDecimal(3);
  // Print row...
}
rs.close();
stmt.close();

#sql private static iterator EmployeeIterator(String, String, BigDecimal);
...
EmployeeIterator iter;
#sql [ctx] iter = {
  SELECT LASTNAME
       , FIRSTNME
       , SALARY
    FROM DSN8710.EMP
   WHERE SALARY BETWEEN :min AND :max
};
do {
  #sql {
    FETCH :iter
     INTO :lastname, :firstname, :salary
  };
  // Print row...
} while (!iter.endFetch());
iter.close();

Single-row query

JDBC

SQLJ

PreparedStatement stmt = conn.prepareStatement(
    "SELECT MAX(SALARY), AVG(SALARY)"
  + " FROM DSN8710.EMP");
rs = stmt.executeQuery();
if (!rs.next()) {
  // Error—no rows found
}
maxSalary = rs.getBigDecimal(1);
avgSalary = rs.getBigDecimal(2);
if (rs.next()) {
  // Error—more than one row found
}
rs.close();
stmt.close();

#sql [ctx] {
  SELECT MAX(SALARY), AVG(SALARY)
    INTO :maxSalary, :avgSalary
    FROM DSN8710.EMP
};

INSERT

JDBC

SQLJ

stmt = conn.prepareStatement(
   "INSERT INTO DSN8710.EMP " +
   "(EMPNO, FIRSTNME, MIDINIT, LASTNAME, HIREDATE, SALARY) "
 + "VALUES (?, ?, ?, ?, CURRENT DATE, ?)");
stmt.setString(1, empno);
stmt.setString(2, firstname);
stmt.setString(3, midinit);
stmt.setString(4, lastname);
stmt.setBigDecimal(5, salary);
stmt.executeUpdate();
stmt.close();

#sql [ctx] {
  INSERT INTO DSN8710.EMP
    (EMPNO,  FIRSTNME,   MIDINIT,  LASTNAME,  HIREDATE,     SALARY)
  VALUES
    (:empno, :firstname, :midinit, :lastname, CURRENT DATE, :salary)
};

References

^ Jim Melton (2003). Advanced SQL: 1999. Morgan Kaufmann. pp. 352–355. ISBN 978-1-55860-677-7.

External links

[Melton2003-1] Jim Melton (2003). Advanced SQL: 1999. Morgan Kaufmann. pp. 352–355. ISBN 978-1-55860-677-7.

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