JDBC杂烩饭

Registering Output Parameters

The type codes in java.sql.Types or oracle.jdbc.OracleTypes identify the

SQL types of the output parameters in the registerOutParameter method of the

java.sql.CallableStatement and

oracle.jdbc.OracleCallableStatement interfaces.

These are the forms that the registerOutputParameter method can take for the

CallableStatement and OracleCallableStatement interfaces

cs.registerOutParameter(int index, int sqlType);
cs.registerOutParameter(int index, int sqlType, String sql_name);
cs.registerOutParameter(int index, int sqlType, int scale);

In these signatures, index represents the parameter index, sqlType is the type code

for the SQL data type, sql_name is the name given to the data type, for user-defined

types, when sqlType is a STRUCT, REF, or ARRAY type code, and scale represents

the number of digits to the right of the decimal point, when sqlType is a NUMERIC or

DECIMAL type code.

setNull Method

The type codes in Types and OracleTypes identify the SQL type of the data item,

which the setNull method sets to NULL. The setNull method can be found in the

java.sql.PreparedStatement and

oracle.jdbc.OraclePreparedStatement interfaces.

These are the forms that the setNull method can take for the PreparedStatement

and OraclePreparedStatement objects:

ps.setNull(int index, int sqlType);
ps.setNull(int index, int sqlType, String sql_name);

In these signatures, index represents the parameter index, sqlType is the type code

for the SQL data type, and sql_name is the name given to the data type, for

user-defined types, when sqlType is a STRUCT, REF, or ARRAY type code. If you enter

an invalid sqlType, a ParameterTypeConflict exception is thrown.

The following example uses a prepared statement to insert a null value into the

database. Note the use of OracleTypes.NUMERIC to identify the numeric object set

to NULL. Alternatively, Types.NUMERIC can be used.

Method setFixedCHAR for Binding CHAR Data into WHERE Clauses

CHAR data in the database is padded to the column width. This leads to a limitation in

using the setCHAR method to bind character data into the WHERE clause of a SELECT

statement. The character data in the WHERE clause must also be padded to the column

width to produce a match in the SELECT statement. This is especially troublesome if

you do not know the column width.

To remedy this, Oracle has added the setFixedCHAR method to the

OraclePreparedStatement class. This method runs a non-padded comparison.

OraclePreparedStatement pstmt=(OraclePreparedStatement) conn.prepareStatement("select count(*) from my_table where col1=?");
pstmt.setFixedCHAR(1, "JDBC");

//or method 2nd
OraclePreparedStatement pstmt=(OraclePreparedStatement) conn.prepareStatement("select count(*) from my_table where trim(col1)=?");
pstmt.setString(1, "JDBC");