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SQL programmingYou can use the HCL OneDB™ implementation of the SQL language to develop applications for HCL OneDB™ database servers.
Guide to SQL: SyntaxThe HCL OneDB™ Guide to SQL: Syntax describes the syntax of the statements, data types, expressions, operators, and built-in functions of the HCL OneDB™ dialect of the SQL language.
SQL statementsThis chapter describes the syntax and semantics of SQL statements that are recognized by HCL OneDB™.
CREATE EXTERNAL TABLE StatementUse the CREATE EXTERNAL TABLE statement to define an external source that is not part of your database to load and unload data for your database.
External Table Examples The examples in this section illustrate different ways to load and unload data using external tables.
Loading Data from External Tables into HCL OneDB™To load data, you define the external data as an external table and then insert the data into the database.
Loading Data Warehousing TablesYou can use external tables to load very large tables for data warehousing applications.
Refreshing Periodically This scenario loads new data in a data warehouse table periodically from some other source.

Refreshing Periodically

This scenario loads new data in a data warehouse table periodically from some other source.

About this task

The scenario assumes that the table is type STANDARD during normal operation and that the CREATE EXTERNAL TABLE statement has been previously executed and the EXPRESS keyword was specified in the USING clause.

To refresh a table periodically

Procedure

Drop all indexes on the table.
Alter the table to type RAW.
```
ALTER TABLE tab1 TYPE(RAW);
```
Load the new data in the table.
```
INSERT INTO tab1 SELECT * FROM ext_tab
```
This insert statement quickly appends new data to the end of the table, and the operation uses very little log space.
Verify the integrity of the data.
Change the table to type STANDARD.
```
ALTER TABLE tab1 TYPE(STANDARD);
```
Re-create indexes on the table so that queries run more quickly.
Perform a level-0 backup to enable you to restore the table later, if necessary. You do not need to perform this level-0 backup if it would be just as easy to reload the table from the original source in the case of a problem.