SQL*Loader, Oracle's data loading tool, has been enhanced for Oracle.
The improvements are significant because they open up the capabilities of SQL*Loader to a wider variety of uses.
The following Slide Show illustrates the SQL*Loader enhancements.
SQL*Loader is invoked when you specify the sqlldr command and, optionally, parameters that establish session characteristics. In situations where you always use the same parameters for which the values seldom change,
it can be more efficient to specify parameters using the following methods, rather than on the command line:
- Parameters can be grouped together in a parameter file. You could then specify the name of the parameter file on the command line using the PARFILE parameter.
- Certain parameters can also be specified within the SQL*Loader control file by using the OPTIONS clause.
Parameters specified on the command line override any parameter values specified in a parameter file or OPTIONS clause.
The control file is a text file written in a language that SQL*Loader understands. The control file tells SQL*Loader where to find the data, how to parse and interpret the data, where to insert the data, and more.
Although not precisely defined, a control file can be said to have three sections. The first section contains session-wide information, for example:
- Global options such as bindsize, rows, records to skip, and so on
- INFILE clauses to specify where the input data is located
- Data to be loaded
The second section consists of one or more INTO TABLE blocks. Each of these blocks contains information about the table into which the data is to be loaded, such as the table name and the columns of the table. The third section is optional and, if present, contains input data. Some control file syntax considerations to keep in mind are:
- The syntax is free-format (statements can extend over multiple lines).
- It is case insensitive; however, strings enclosed in single or double quotation marks are taken literally, including case.
- In control file syntax, comments extend from the two hyphens (--) that mark the beginning of the comment to the end of the line.
The optional third section of the control file is interpreted as data rather than as control file syntax; consequently, comments in this section are not supported.
- The keywords CONSTANT and ZONE have special meaning to SQL*Loader and are therefore reserved. To avoid potential conflicts, Oracle recommends that you do not use either CONSTANT or ZONE as a name for any tables or columns.
The next lesson demonstrates two of the new features of SQL*Loader.