Skip Headers

Oracle® Database JDBC Developer's Guide and Reference
10g Release 1 (10.1)

Part Number B10979-02
Go to Documentation Home
Home
Go to Book List
Book List
Go to Table of Contents
Contents
Go to Index
Index
Go to Master Index
Master Index
Go to Feedback page
Feedback

Go to previous page
Previous
Go to next page
Next
View PDF

25 Reference Information

This chapter contains detailed JDBC reference information, including the following topics:

25.1 Valid SQL-JDBC Datatype Mappings

Table 4-3 in Chapter 4 describes the default mappings between Java classes and SQL datatypes supported by the Oracle JDBC drivers. Compare the contents of the JDBC Datatypes, Standard Java Types, and SQL Datatypes columns in Table 4-3 with the contents of Table 25-1 below.

Table 25-1 lists all the possible Java types to which a given SQL datatype can be validly mapped. The Oracle JDBC drivers will support these "non-default" mappings. For example, to materialize SQL CHAR data in an oracle.sql.CHAR object use the getCHAR() method. To materialize it as a java.math.BigDecimal object, use the getBigDecimal() method.


Notes:

For classes where oracle.sql.ORAData appears in italic, these can be generated by JPublisher.

Table 25-1 Valid SQL Datatype-Java Class Mappings

These SQL datatypes: Can be materialized as these Java types:
CHAR, VARCHAR2, LONG oracle.sql.CHAR

java.lang.String

java.sql.Date

java.sql.Time

java.sql.Timestamp

java.lang.Byte

java.lang.Short

java.lang.Integer

java.lang.Long

java.lang.Float

java.lang.Double

java.math.BigDecimal

byte, short, int, long, float, double
DATE oracle.sql.DATE

java.sql.Date

java.sql.Time

java.sql.Timestamp

java.lang.String
NUMBER oracle.sql.NUMBER

java.lang.Byte

java.lang.Short

java.lang.Integer

java.lang.Long

java.lang.Float

java.lang.Double

java.math.BigDecimal

byte, short, int, long, float, double
OPAQUE oracle.sql.OPAQUE
RAW, LONG RAW oracle.sql.RAW
  byte[]
ROWID oracle.sql.CHAR

oracle.sql.ROWID

java.lang.String
BFILE oracle.sql.BFILE
BLOB oracle.sql.BLOB

java.sql.Blob
CLOB oracle.sql.CLOB

java.sql.Clob
TIMESTAMP java.sql.Date, oracle.sql.DATE, java.sql.Time, java.sql.Timestamp, oracle.sql.TIMESTAMP, java.lang.String, byte[]
TIMESTAMP WITH TIME ZONE java.sql.Date, oracle.sql.DATE, java.sql.Time, java.sql.Timestamp, oracle.sql.TIMESTAMPTZ, java.lang.String, byte[]
TIMESTAMP WITH LOCAL TIME ZONE java.sql.Date, oracle.sql.DATE, java.sql.Time, java.sql.Timestamp, oracle.sql.TIMESTAMPLTZ, java.lang.String, byte[]
Object types oracle.sql.STRUCT

java.sql.Struct

java.sql.SqlData

oracle.sql.ORAData
Reference types oracle.sql.REF

java.sql.Ref

oracle.sql.ORAData
Nested table types and VARRAY types oracle.sql.ARRAY

java.sql.Array

oracle.sql.ORAData

Notes:

  • The type UROWID is not supported.

  • The oracle.sql.Datum class is abstract. The value passed to a parameter of type oracle.sql.Datum must be of the Java type corresponding to the underlying SQL type. Likewise, the value returned by a method with return type oracle.sql.Datum must be of the Java type corresponding to the underlying SQL type.

  • The mappings to oracle.sql classes are optimal if no conversion from SQL format to Java format is necessary.

25.2 Supported SQL and PL/SQL Datatypes

The tables in this section list SQL and PL/SQL datatypes, and whether the Oracle JDBC drivers support them. Table 25-2 describes Oracle JDBC driver support for SQL datatypes.

Table 25-2 Support for SQL Datatypes

SQL Datatype Supported by JDBC Drivers?
BFILE yes
BLOB yes
CHAR yes
CLOB yes
DATE yes
NCHAR no (see Note)
NCHAR VARYING no
NUMBER yes
NVARCHAR2 no (see Note)
RAW yes
REF yes
ROWID yes
UROWID no
VARCHAR2 yes

Note:

The types NCHAR and NVARCHAR2 are supported indirectly. There is no corresponding java.sql.Types type (use CHAR), but if your application invokes formOfUse(NCHAR) then these types can be accessed. See "NCHAR, NVARCHAR2, NCLOB and the defaultNChar Property" for details.

Table 25-3 describes Oracle JDBC support for the ANSI-supported SQL datatypes.

Table 25-3 Support for ANSI-92 SQL Datatypes

ANSI-Supported SQL Datatype Supported by JDBC Drivers?
CHARACTER yes
DEC yes
DECIMAL yes
DOUBLE PRECISION yes
FLOAT yes
INT yes
INTEGER yes
NATIONAL CHARACTER no
NATIONAL CHARACTER VARYING no
NATIONAL CHAR yes
NATIONAL CHAR VARYING no
NCHAR yes
NCHAR VARYING no
NUMERIC yes
REAL yes
SMALLINT yes
VARCHAR yes

Table 25-4 describes Oracle JDBC driver support for SQL User-Defined types.

Table 25-4 Support for SQL User-Defined Types

SQL User-Defined type Supported by JDBC Drivers?
OPAQUE yes
Reference types yes
Object types (JAVA_OBJECT) yes
Nested table types and VARRAY types yes

Table 25-5 describes Oracle JDBC driver support for PL/SQL datatypes. Note that PL/SQL datatypes include these categories:

Table 25-5 Support for PL/SQL Datatypes

PL/SQL Datatype Supported by JDBC Drivers?
Scalar Types:
BINARY INTEGER yes
DEC yes
DECIMAL yes
DOUBLE PRECISION yes
FLOAT yes
INT yes
INTEGER yes
NATURAL yes
NATURALn no
NUMBER yes
NUMERIC yes
PLS_INTEGER yes
POSITIVE yes
POSITIVEn no
REAL yes
SIGNTYPE yes
SMALLINT yes
Scalar Character Types:
CHAR yes
CHARACTER yes
LONG yes
LONG RAW yes
NCHAR no (see Note)
NVARCHAR2 no (see Note)
RAW yes
ROWID yes
STRING yes
UROWID no
VARCHAR yes
VARCHAR2 yes
BOOLEAN yes
DATE yes
Composite Types:
RECORD no
TABLE no
VARRAY yes
Reference Types:
REF CURSOR types yes
object reference types yes
LOB Types:
BFILE yes
BLOB yes
CLOB yes
NCLOB yes

Notes:

  • The types NATURAL, NATURALn, POSITIVE, POSITIVEn, and SIGNTYPE are subtypes of BINARY INTEGER.

  • The types DEC, DECIMAL, DOUBLE PRECISION, FLOAT, INT, INTEGER, NUMERIC, REAL, and SMALLINT are subtypes of NUMBER.

  • The types NCHAR and NVARCHAR2 are supported indirectly. There is no corresponding java.sql.Types type (use CHAR), but if your application invokes formOfUse(NCHAR) then these types can be accessed. See "NCHAR, NVARCHAR2, NCLOB and the defaultNChar Property" for details.

25.3 Embedded SQL92 Syntax

Oracle's JDBC drivers support some embedded SQL92 syntax (the syntax that you specify between curly braces). The current support is basic. This section describes the support offered by the drivers for the following SQL92 constructs:

Where driver support is limited, these sections also describe possible workarounds.

25.3.1 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);


Note:

Call PreparedStatement.setEscapeProcessing() immediately after creating a statement. If you call this method after the SQL text has already been processed for escapes, a SQLException will be thrown.

25.3.2 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.

25.3.2.1 Date Literals

The JDBC drivers support date literals in SQL statements written in the format:

{d 'yyyy-mm-dd'}

Where yyyy-mm-dd represents the year, month, and day—for example:

{d '1995-10-22'}

The JDBC drivers will replace this escape clause with the equivalent Oracle representation: "22 OCT 1995".

This code snippet contains an example of using a date literal in a SQL statement.

// 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));

25.3.2.2 Time Literals

The JDBC drivers support time literals in SQL statements written in the format:

{t 'hh:mm:ss'}

where hh:mm:ss represents the hours, minutes, and seconds—for example:

{t '05:10:45'}

The JDBC drivers will replace this escape clause with the equivalent Oracle representation: "05:10:45".

If the time is specified as:

{t '14:20:50'}

Then the equivalent Oracle representation would be "14:20:50", assuming the server is using a 24-hour clock.

This code snippet contains an example of using a time literal in a SQL statement.

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

25.3.2.3 Timestamp Literals

The JDBC drivers support timestamp literals in SQL statements written in the format:

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

where yyyy-mm-dd hh:mm:ss.f... represents the year, month, day, hours, minutes, and seconds. The fractional seconds portion (.f...) is optional and can be omitted. For example: {ts '1997-11-01 13:22:45'} represents, in Oracle format, NOV 01 1997 13:22:45.

This code snippet contains an example of using a timestamp literal in a SQL statement.

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

25.3.3 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.

25.3.4 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));


Note:

If you want to use the backslash character (\) as an escape character, you must enter it twice (that is, \\). For example:
ResultSet rset = stmt.executeQuery("SELECT empno FROM emp
                WHERE ename LIKE '\\_%' {escape '\\'}");

25.3.5 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");

25.3.6 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,...) }

25.3.7 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') 

25.4 Oracle JDBC Notes and Limitations

The following limitations exist in the Oracle JDBC implementation, but all of them are either insignificant or have easy workarounds.

25.4.1 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".

25.4.2 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".

25.4.3 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".

25.4.4 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.

25.4.5 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".

25.4.6 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".

25.4.7 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" .

25.4.7.1 Retaining Bound Values

Before Oracle9i, the Oracle JDBC drivers did not retain bound values from one call of execute to the next as specified in JDBC 1.0. All releases after Oracle9i have retained bound values. For example:

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();  

Previously, a SQLException would be thrown by the second execute() call because no value was bound to the second argument. In this release, the second execute will return the correct value, retaining the binding of the second argument to the string "SALES".

If the retained bound value is a stream, then the Oracle JDBC drivers will not reset the stream. Unless the application code resets, repositions, or otherwise modifies the stream, the subsequent execute calls will send NULL as the value of the argument.