12.3. Attributes for Handles | MYSQL in a Nutshell (In a Nutshell (OReilly))

This section lists the values that can be added to the optional %attributes hash that appears in many Perl DBI methods. The basic syntax to set an attribute is $handle->{attribute} = 'setting'; to retrieve a setting use $handle->{attribute}.

12.3.1. Attributes for All Handles

You can use the following attributes with both database handles and statement handles.

Active: Instructs the server that the handle should remain open until terminated explicitly by finish() or disconnect( ) depending on the handle type.
ActiveKids: Provides the number of active handles under the handle that employed the attribute. If it's set by a database handle, then the number of active statement handles will be returned. If it's called by a database handle, the number of active statement handles will be returned. If set by a driver handle, the number of database handles will be returned.
CacheKids: Returns a reference to a hash containing child handles for a driver or a database handle that was created by the connect_cached( ) or prepare_cached( ) methods, respectively.
ChopBlanks: Trims trailing spaces from fixed-width character columns.
CompatMode: Makes emulation layers compatible with a driver handle.
ErrCount: Counts the number of errors logged by set_err( ).
Executed: Determines whether a handle or one of its children has been executed.
FetchHashKeyName: Instructs fetchrow_hashref() calls to convert column names to either all lowercase (NAME_lc) or all uppercase (NAME_uc) letters.
HandleError: Customizes the response to an error caused by the handle. You could use this attribute to run a subroutine in the event of an error.
HandleSetErr: Customizes the settings of an error caused by the handle. It's similar to the HandleError attribute, but it relates to set_err( ).
InactiveDestroy: Prevents the server from destroying a handle that is out of scope, unless it is closed intentionally with a function like finish( ) or disconnect( ).
Kids: Provides the number of all handles (active and inactive) under the handle that employed the attribute. If it's called by a database handle, the number of statement handles will be returned. If it's called by a driver handle, the number of database handles will be returned.
LongReadLen: Sets the maximum length of data retrieved from long datatype columns (i.e., BLOB and TEXT).
LongTruncOK: Prevents a fetch method from failing if a column's data exceeds the maximum length by the LongReadLen attribute.
PrintError: Obtains error codes and error messages associated with the handle.
PrintWarn: Controls the warning messages that are logged.
private_*: Stores information on the handle as a private attribute with a customized name starting with private_.
Profile: Enables logging of method call timing statistics.
RaiseError: Raises exceptions when errors are associated with the handle.
ShowErrorStatement: Specifies text to append to error messages caused by the PrintError, PrintWarn, and RaiseError attributes.
Taint: Combines TaintIn and TaintOut attributes.
TaintIn: Instructs DBI to check if method calls are tainted, when Perl is run in taint mode.
TaintOut: Instructs DBI to assume that data fetched is tainted, when Perl is running in taint mode.
TraceLevel: Sets trace levels and flags for a handle. It's an alternative to the trace() method.
Warn: Enables or disables warning messages for poor database procedures.

12.3.2. Attributes Only for Database Handles

AutoCommit: Allows the rollback( ) function to be used if attribute is 0.
Driver: Provides the name of the parent driver.
Name: Provides the name of the database for the database handle.
RowCacheSize: Provides a suggested cache size for rows generated for SELECT statements. If it's 0, DBI automatically determines the cache size. A value of 1 disables local row caching.
Statement: Provides the last SQL statement prepared with the database handle regardless of whether it succeeded.
Username: Provides the name of the user for the database handle.

12.3.3. Attributes Only for Statement Handles

CursorName: Sets the name of the cursor for the statement handle.
Database: Provides the database handle of the statement handle.
Name: Contains a reference to an array containing the names of the columns of the SQL statement from the statement handle.
NULLABLE: Contains a reference to an array indicating whether each column in the SQL statement of the handle may contain a NULL value.
NUM_OF_FIELDS: Returns the number of columns in the SQL statement of the handle.
NUM_OF_PARAMS: Returns the number of placeholders in the SQL statement of the handle.
ParamValues: Returns a reference to a hash of bound parameters and their values.
Statement: Is the SQL statement passed to prepare( ).
TYPE: Contains a reference to an array of codes for international standard values for data-types (e.g., 1 for SQL_CHAR, 4 for SQL_INTEGER).
PRECISION: Contains a reference to an array containing the length of columns (as set in the table definition) in the SQL statement of the handle.
SCALE: Contains a reference to an array containing the number of decimal places for columns in the SQL statement of the handle.

12.3.4. DBI Dynamic Attributes

These attributes are related to the last handle used, regardless of the type of handle. The syntax of each of these is $DBI::attribute.

err: Is synonymous with $handle->err.
errstr: Is synonymous with $handle->errstr.
lasth: Returns the handle used by the last method call.
rows: Is synonymous with $handle->rows.
state: Is synonymous with $handle->state.