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java.lang.Objectorg.hsqldb.jdbc.JDBCResultSetMetaData
public class JDBCResultSetMetaData
An object that can be used to get information about the types
and properties of the columns in a ResultSet object.
The following code fragment creates the ResultSet object rs,
creates the ResultSetMetaData object rsmd, and uses rsmd
to find out how many columns rs has and whether the first column in rs
can be used in a WHERE clause.
ResultSet rs = stmt.executeQuery("SELECT a, b, c FROM TABLE2");
ResultSetMetaData rsmd = rs.getMetaData();
int numberOfColumns = rsmd.getColumnCount();
boolean b = rsmd.isSearchable(1);
HSQLDB supports a subset of the ResultSetMetaData interface.
The JDBC specification for ResultSetMetaData is in part very
vague. This causes potential incompatibility between interpretations of the
specification as realized in different JDBC driver implementations. As such,
deciding to what degree reporting ResultSetMetaData is accurate has been
considered very carefully. Hopefully, the design decisions made in light of
these considerations have yeilded precisely the subset of full
ResultSetMetaData support that is most commonly needed and that is most
important, while also providing, under the most common use-cases, the
fastest access with the least overhead and the best comprimise between
speed, accuracy, jar-footprint and retention of JDBC resources.
(fredt@users)
(boucherb@users)
JDBCStatement.executeQuery(java.lang.String),
JDBCStatement.getResultSet(),
ResultSetMetaData| Field Summary |
|---|
| Fields inherited from interface java.sql.ResultSetMetaData |
|---|
columnNoNulls, columnNullable, columnNullableUnknown |
| Method Summary | ||
|---|---|---|
String |
getCatalogName(int column)
Gets the designated column's table's catalog name. |
|
String |
getColumnClassName(int column)
|
|
int |
getColumnCount()
Returns the number of columns in this ResultSet object. |
|
int |
getColumnDisplaySize(int column)
Indicates the designated column's normal maximum width in characters. |
|
String |
getColumnLabel(int column)
Gets the designated column's suggested title for use in printouts and displays. |
|
String |
getColumnName(int column)
Get the designated column's name. |
|
int |
getColumnType(int column)
Retrieves the designated column's SQL type. |
|
String |
getColumnTypeName(int column)
Retrieves the designated column's database-specific type name. |
|
int |
getPrecision(int column)
(JDBC4 clarification:) Get the designated column's specified column size. |
|
int |
getScale(int column)
Gets the designated column's number of digits to right of the decimal point. |
|
String |
getSchemaName(int column)
Get the designated column's table's schema. |
|
String |
getTableName(int column)
Gets the designated column's table name. |
|
boolean |
isAutoIncrement(int column)
Indicates whether the designated column is automatically numbered. |
|
boolean |
isCaseSensitive(int column)
Indicates whether a column's case matters. |
|
boolean |
isCurrency(int column)
Indicates whether the designated column is a cash value. |
|
boolean |
isDefinitelyWritable(int column)
Indicates whether a write on the designated column will definitely succeed. |
|
int |
isNullable(int column)
Indicates the nullability of values in the designated column. |
|
boolean |
isReadOnly(int column)
Indicates whether the designated column is definitely not writable. |
|
boolean |
isSearchable(int column)
Indicates whether the designated column can be used in a where clause. |
|
boolean |
isSigned(int column)
Indicates whether values in the designated column are signed numbers. |
|
boolean |
isWrapperFor(Class<?> iface)
Returns true if this either implements the interface argument or is directly or indirectly a wrapper for an object that does. |
|
boolean |
isWritable(int column)
Indicates whether it is possible for a write on the designated column to succeed. |
|
String |
toString()
Returns a string representation of the object. |
|
|
unwrap(Class<T> iface)
Returns an object that implements the given interface to allow access to non-standard methods, or standard methods not exposed by the proxy. |
|
| Methods inherited from class java.lang.Object |
|---|
equals, getClass, hashCode, notify, notifyAll, wait, wait, wait |
| Method Detail |
|---|
public int getColumnCount()
throws SQLException
ResultSet object.
getColumnCount in interface ResultSetMetaDataSQLException - if a database access error occurs
public boolean isAutoIncrement(int column)
throws SQLException
(JDBC4 deleted:)[, thus read-only.]
HSQLDB 2.0 fully supports SQL Satandard features T174 and T176 that define identity column support.
In fact, the generic documentation previous to the JDBC4 specification seems to contradict the general definition of what, at minimum, an auto-increment column is:
Simply, an auto-increment column is one that guarantees it has a autogenerated value after a successful insert or update operation, even if no value is supplied, or DEFAULT is specified.
isAutoIncrement in interface ResultSetMetaDatacolumn - the first column is 1, the second is 2, ...
true if so; false otherwise
SQLException - if a database access error occurs
public boolean isCaseSensitive(int column)
throws SQLException
HSQLDB 1.7.1 did not report this value accurately.
Starting with 1.7.2, this feature is better supported.
This method returns true for any column whose data type is a character type, with the exception of VARCHAR_IGNORECASE for which it returns false. It also returns false for any column whose data type is a not a character data type.
isCaseSensitive in interface ResultSetMetaDatacolumn - the first column is 1, the second is 2, ...
true if so; false otherwise
SQLException - if a database access error occurs
public boolean isSearchable(int column)
throws SQLException
HSQLDB 2.0 handles this differently from previous versions.
If the column in question is a database table or view column, and the type of the column allows searching, then returns true, otherwise false.
isSearchable in interface ResultSetMetaDatacolumn - the first column is 1, the second is 2, ...
true if so; false otherwise
SQLException - if a database access error occurs
public boolean isCurrency(int column)
throws SQLException
HSQLDB 2.0 fully supports this feature and returns true for NUMERIC and DECIMAL columns.
isCurrency in interface ResultSetMetaDatacolumn - the first column is 1, the second is 2, ...
true if so; false otherwise
SQLException - if a database access error occurs
public int isNullable(int column)
throws SQLException
HSQLDB 2.2 fully supports this feature.
columnNoNulls is always returned for result set columns that represent constants, sequences or table columns known to be not null. columnNullable is returned for NULL constants, or nullable table columns. columnNullableUnknown is returned for all other columns such as aggregates and computed values.
To determine the nullable status of a table column in isolation from ResultSetMetaData and in a DBMS-independent fashion, the DatabaseMetaData.getColumns() method can be invoked with the appropriate filter values and the result should be inspected at the position described in the DatabaseMetaData.getColumns() API documentation.
isNullable in interface ResultSetMetaDatacolumn - the first column is 1, the second is 2, ...
columnNoNulls,
columnNullable or columnNullableUnknown
SQLException - if a database access error occurs
public boolean isSigned(int column)
throws SQLException
HSQLDB 2.0 fully supports this feature.
isSigned in interface ResultSetMetaDatacolumn - the first column is 1, the second is 2, ...
true if so; false otherwise
SQLException - if a database access error occurs
public int getColumnDisplaySize(int column)
throws SQLException
HSQLDB 2.0 fully supports this feature.
The current calculation follows these rules:
The maximum length/precision, repectively.
The max precision, plus the length of the negation character (1), plus (if applicable) the maximum number of characters that may occupy the exponent character sequence. Note that some legacy tools do not correctly handle BIGINT values of greater than 18 digits.
The length of the character sequence "false" (5), the longer of the two boolean value String representations.
The maximum length/precision, respectively, as reported by DatabaseMetaData.getTypeInfo(), when applicable. If the maximum display size is unknown, unknowable or inapplicable, then zero is returned.
getColumnDisplaySize in interface ResultSetMetaDatacolumn - the first column is 1, the second is 2, ...
SQLException - if a database access error occurs
public String getColumnLabel(int column)
throws SQLException
AS
clause. If a SQL AS is not specified, the value returned from
getColumnLabel will be the same as the value returned by the
getColumnName method.
In HSQLDB, a ResultSet column label is determined using the
following order of precedence:
getColumnLabel in interface ResultSetMetaDatacolumn - the first column is 1, the second is 2, ...
SQLException - if a database access error occurs
public String getColumnName(int column)
throws SQLException
In HSQLDB, a ResultSet column name is determined using the following order of prcedence:
If the jdbc.get_column_name property of the JDBC Connection
has been set to false, this method returns the same value as
getColumnLabel(int).
getColumnName in interface ResultSetMetaDatacolumn - the first column is 1, the second is 2, ...
SQLException - if a database access error occurs
public String getSchemaName(int column)
throws SQLException
Since 1.8.0.x, HSQLDB implements standard SQL SCHEMA support; this method returns the actual schema of the column's table. Columns generated in queries have no schema name.
getSchemaName in interface ResultSetMetaDatacolumn - the first column is 1, the second is 2, ...
SQLException - if a database access error occurs
public int getPrecision(int column)
throws SQLException
HSQLDB 2.0 reports the correct length or precision for all columns. For DOUBLE, the binary precision of 64 is returned, while for other numeric types the decimal precision is returned.
getPrecision in interface ResultSetMetaDatacolumn - the first column is 1, the second is 2, ...
SQLException - if a database access error occurs
public int getScale(int column)
throws SQLException
HSQLDB 2.0 reports the correct scale for all columns.
For datetime and interval types such as Timestamp or Time, the fractional second precision is reported.
The reported scale for INTEGER, BIGINT and DOUBLE is 0
getScale in interface ResultSetMetaDatacolumn - the first column is 1, the second is 2, ...
SQLException - if a database access error occurs
public String getTableName(int column)
throws SQLException
getTableName in interface ResultSetMetaDatacolumn - the first column is 1, the second is 2, ...
SQLException - if a database access error occurs
public String getCatalogName(int column)
throws SQLException
From 2.0, HSQLDB returns the name of the catalog. The default name is PUBLIC. This value can be changed for the database using an SQL command.
HSQLDB supports use of catalog qualification in DLL or DML when it is allowed by the Standard.
However, not all clients respect the SQL Standard and may use a catalog qualifier in a context where it is not suppoted by the Standard.
For greater detail, see discussion at:
JDBCDatabaseMetaData.
getCatalogName in interface ResultSetMetaDatacolumn - the first column is 1, the second is 2, ...
SQLException - if a database access error occurs
public int getColumnType(int column)
throws SQLException
This reports the SQL type code of the column. For time and timestamp types that are WITH TIME ZONE, the values as the SQL Standarc CLI codes.
getColumnType in interface ResultSetMetaDatacolumn - the first column is 1, the second is 2, ...
SQLException - if a database access error occursTypes
public String getColumnTypeName(int column)
throws SQLException
getColumnTypeName in interface ResultSetMetaDatacolumn - the first column is 1, the second is 2, ...
SQLException - if a database access error occurs
public boolean isReadOnly(int column)
throws SQLException
From 2.0 this method returns true if the ResuleSet is not updatable or the column in question is not updatable.
isReadOnly in interface ResultSetMetaDatacolumn - the first column is 1, the second is 2, ...
true if so; false otherwise
SQLException - if a database access error occurs
public boolean isWritable(int column)
throws SQLException
From 2.0 this method returns false if the ResuleSet is not updatable or the column in question is not updatable.
isWritable in interface ResultSetMetaDatacolumn - the first column is 1, the second is 2, ...
true if so; false otherwise
SQLException - if a database access error occurs
public boolean isDefinitelyWritable(int column)
throws SQLException
From 2.0 this method returns false if the ResuleSet is not updatable or the column in question is not updatable.
isDefinitelyWritable in interface ResultSetMetaDatacolumn - the first column is 1, the second is 2, ...
true if so; false otherwise
SQLException - if a database access error occurs
public String getColumnClassName(int column)
throws SQLException
Returns the fully-qualified name of the Java class whose instances
are manufactured if the method ResultSet.getObject
is called to retrieve a value
from the column. ResultSet.getObject may return a subclass of the
class returned by this method.
HSQLDB 2.0 fully supports this feature.
For columns of type OTHER, there is no specific class name and java.lang.Object is returned.
getColumnClassName in interface ResultSetMetaDatacolumn - the first column is 1, the second is 2, ...
ResultSet.getObject to retrieve the value in the specified
column. This is the class name used for custom mapping.
SQLException - if a database access error occurs
public <T> T unwrap(Class<T> iface)
throws SQLException
unwrap recursively on the wrapped object
or a proxy for that result. If the receiver is not a
wrapper and does not implement the interface, then an SQLException is thrown.
unwrap in interface Wrapperiface - A Class defining an interface that the result must implement.
SQLException - If no object found that implements the interface
public boolean isWrapperFor(Class<?> iface)
throws SQLException
isWrapperFor on the wrapped
object. If this does not implement the interface and is not a wrapper, return false.
This method should be implemented as a low-cost operation compared to unwrap so that
callers can use this method to avoid expensive unwrap calls that may fail. If this method
returns true then calling unwrap with the same argument should succeed.
isWrapperFor in interface Wrapperiface - a Class defining an interface.
SQLException - if an error occurs while determining whether this is a wrapper
for an object with the given interface.public String toString()
The string consists of the name of the class of which the
object is an instance, the at-sign character `@',
the unsigned hexadecimal representation of the hash code of the
object and a comma-delimited list of this object's indexed attributes,
enclosed in square brakets.
toString in class Object
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