24 Reference Information

Disabling Escape Processing

Escape processing for SQL92 syntax is enabled by default, which results in the JDBC driver performing escape substitution before sending the SQL code to the database. If you want the driver to use regular Oracle SQL syntax, which is more efficient than SQL92 syntax and escape processing, then use this statement:

stmt.setEscapeProcessing(false);

Time and Date Literals

Databases differ in the syntax they use for date, time, and timestamp literals. JDBC supports dates and times written only in a specific format. This section describes the formats you must use for date, time, and timestamp literals in SQL statements.

{d 'yyyy-mm-dd'}

{d '1995-10-22'}

// Connect to the database
// You can put a database name after the @ sign in the connection URL.
OracleDataSource ods = new OracleDataSource();
ods.setURL("jdbc:oracle:oci:@");
ods.setUser("scott");
ods.setPassword("tiger");
Connection conn = ods.getConnection();

// Create a Statement
Statement stmt = conn.createStatement ();

// Select the ename column from the emp table where the hiredate is Jan-23-1982
ResultSet rset = stmt.executeQuery 
                 ("SELECT ename FROM emp WHERE hiredate = {d '1982-01-23'}");

// Iterate through the result and print the employee names
while (rset.next ())
   System.out.println (rset.getString (1));

{t 'hh:mm:ss'}

{t '05:10:45'}

{t '14:20:50'}

ResultSet rset = stmt.executeQuery 
                 ("SELECT ename FROM emp WHERE hiredate = {t '12:00:00'}");

{ts 'yyyy-mm-dd hh:mm:ss.f...'} 

ResultSet rset = stmt.executeQuery 
    ("SELECT ename FROM emp WHERE hiredate = {ts '1982-01-23 12:00:00'}");

Scalar Functions

The Oracle JDBC drivers do not support all scalar functions. To find out which functions the drivers support, use the following methods supported by the Oracle-specific oracle.jdbc.OracleDatabaseMetaData class and the standard Java java.sql.DatabaseMetadata interface:

• getNumericFunctions(): Returns a comma-separated list of math functions supported by the driver. For example, ABS, COS, SQRT.

• getStringFunctions(): Returns a comma-separated list of string functions supported by the driver. For example, ASCII, LOCATE.

• getSystemFunctions(): Returns a comma-separated list of system functions supported by the driver. For example, DATABASE, USER.

• getTimeDateFunctions(): Returns a comma-separated list of time and date functions supported by the driver. For example, CURDATE, DAYOFYEAR, HOUR.

  
  

  Note: Oracle's JDBC drivers support fn, the function keyword.

  
  

LIKE Escape Characters

The characters "%" and "_" have special meaning in SQL LIKE clauses (you use "%" to match zero or more characters, "_" to match exactly one character). If you want to interpret these characters literally in strings, you precede them with a special escape character. For example, if you want to use the ampersand "&" as the escape character, you identify it in the SQL statement as {escape '&'}:

Statement stmt = conn.createStatement ();

// Select the empno column from the emp table where the ename starts with '_'
ResultSet rset = stmt.executeQuery
          ("SELECT empno FROM emp WHERE ename LIKE '&_%' {ESCAPE '&'}");

// Iterate through the result and print the employee numbers
while (rset.next ())
   System.out.println (rset.getString (1));

ResultSet rset = stmt.executeQuery("SELECT empno FROM emp
             WHERE ename LIKE '\\_%' {escape '\\'}");

Outer Joins

Oracle's JDBC drivers do not support outer join syntax: {oj outer-join}. The workaround is to use Oracle outer join syntax:

Instead of:

Statement stmt = conn.createStatement ();
ResultSet rset = stmt.executeQuery
     ("SELECT ename, dname 
       FROM {OJ dept LEFT OUTER JOIN emp ON dept.deptno = emp.deptno} 
       ORDER BY ename");

Use Oracle SQL syntax:

Statement stmt = conn.createStatement ();
ResultSet rset = stmt.executeQuery
     ("SELECT ename, dname 
       FROM emp a, dept b WHERE a.deptno = b.deptno(+)
       ORDER BY ename");

Function Call Syntax

Oracle's JDBC drivers support the following procedure and function call syntax:

Procedure calls (without a return value):

{ call procedure_name (argument1, argument2,...) } 

Function calls (with a return value):

{ ? = call procedure_name (argument1, argument2,...) }

SQL92 to SQL Syntax Example

You can write a simple program to translate SQL92 syntax to standard SQL syntax. The following program prints the comparable SQL syntax for SQL92 statements for function calls, date literals, time literals, and timestamp literals. In the program, the oracle.jdbc.OracleSql class parse() method performs the conversions.

import oracle.jdbc.OracleSql; 
 
public class Foo 
{ 
   public static void main (String args[]) throws Exception 
   { 
      show ("{call foo(?, ?)}"); 
      show ("{? = call bar (?, ?)}"); 
      show ("{d '1998-10-22'}"); 
      show ("{t '16:22:34'}"); 
      show ("{ts '1998-10-22 16:22:34'}"); 
   } 
 
   public static void show (String s) throws Exception 
   { 
      System.out.println (s + " => " + 
         oracle.jdbc.OracleDriver.processSqlEscapes(s)); 
   } 
}

The following code is the output that prints the comparable SQL syntax.

{call foo(?, ?)} => BEGIN foo(:1, :2); END; 
{? = call bar (?, ?)} => BEGIN :1 := bar (:2, :3); END; 
{d '1998-10-22'} => TO_DATE ('1998-10-22', 'YYYY-MM-DD') 
{t '16:22:34'} => TO_DATE ('16:22:34', 'HH24:MI:SS') 
{ts '1998-10-22 16:22:34'} => TO_DATE ('1998-10-22 16:22:34', 'YYYY-MM-DD 
HH24:MI:SS') 

CursorName

Oracle JDBC drivers do not support the get getCursorName() and setCursorName() methods, because there is no convenient way to map them to Oracle constructs. Oracle recommends using ROWID instead. For more information on how to use and manipulate ROWIDs, see "Oracle ROWID Type".

SQL92 Outer Join Escapes

Oracle JDBC drivers do not support SQL92 outer join escapes. Use Oracle SQL syntax with "(+)" instead. For more information on SQL92 syntax, see "Embedded SQL92 Syntax".

PL/SQL TABLE, BOOLEAN, and RECORD Types

It is not feasible for Oracle JDBC drivers to support calling arguments or return values of the PL/SQL RECORD, BOOLEAN, or table with non-scalar element types. However, Oracle JDBC drivers support PL/SQL index-by table of scalar element types. For a complete description of this, see "Accessing PL/SQL Index-by Tables".

As a workaround to PL/SQL RECORD, BOOLEAN, or non-scalar table types, create wrapper procedures that handle the data as types supported by JDBC. For example, to wrap a stored procedure that uses PL/SQL booleans, create a stored procedure that takes a character or number from JDBC and passes it to the original procedure as BOOLEAN or, for an output parameter, accepts a BOOLEAN argument from the original procedure and passes it as a CHAR or NUMBER to JDBC. Similarly, to wrap a stored procedure that uses PL/SQL records, create a stored procedure that handles a record in its individual components (such as CHAR and NUMBER) or in a structured object type. To wrap a stored procedure that uses PL/SQL tables, break the data into components or perhaps use Oracle collection types.

For an example of a workaround for BOOLEAN, see "Boolean Parameters in PL/SQL Stored Procedures".

IEEE 754 Floating Point Compliance

The arithmetic for the Oracle NUMBER type does not comply with the IEEE 754 standard for floating-point arithmetic. Therefore, there can be small disagreements between the results of computations performed by Oracle and the same computations performed by Java.

Oracle stores numbers in a format compatible with decimal arithmetic and guarantees 38 decimal digits of precision. It represents zero, minus infinity, and plus infinity exactly. For each positive number it represents, it represents a negative number of the same absolute value.

It represents every positive number between 10^-30 and (1 – 10^-38) * 10¹²⁶ to full 38-digit precision.

Catalog Arguments to DatabaseMetaData Calls

Certain DatabaseMetaData methods define a catalog parameter. This parameter is one of the selection criteria for the method. Oracle does not have multiple catalogs, but it does have packages. For more information on how the Oracle JDBC drivers treat the catalog argument, see "DatabaseMetaData TABLE_REMARKS Reporting".

SQLWarning Class

The java.sql.SQLWarning class provides information on a database access warning. Warnings typically contain a description of the warning and a code that identifies the warning. Warnings are silently chained to the object whose method caused it to be reported. The Oracle JDBC drivers generally do not support SQLWarning. (As an exception to this, scrollable result set operations do generate SQL warnings, but the SQLWarning instance is created on the client, not in the database.)

For information on how the Oracle JDBC drivers handle errors, see "Processing SQL Exceptions".

Binding Named Parameters

Binding by name is not supported when using the setXXX methods. Under certain circumstances, previous versions of the Oracle JDBC drivers have allowed binding statement variables by name when using the setXXX methods. In the following statement, the named variable EmpId would be bound to the integer 314159.

PreparedStatement p = conn.prepareStatement
  ("SELECT name FROM emp WHERE id = :EmpId");
  p.setInt(1, 314159);

This capability to bind by name using the setXXX methods is not part of the JDBC specification, and Oracle does not support it. The JDBC drivers can throw a SQLException or produce unexpected results. In 10g Release 1 (10.1) JDBC drivers, bind by name is supported using the setXXXAtName methods. See "Interface oracle.jdbc.OracleCallableStatement" and "Interface oracle.jdbc.OraclePreparedStatement" .

PreparedStatement p = conn.prepareStatement
    ("SELECT name FROM emp WHERE id = ? AND dept = ?");
p.setInt(1, 314159); 
p.setString(2, "SALES"); 
ResultSet r1 = p.execute(); 
p.setInt(1, 425260); 
ResultSet r2 = p.execute();