D191 advanced data PDF

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D191 page 1 The load is the last step of ETL process - involves importing extracted and transformed data into a target database or data warehouse. Some load processes physically insert each record as a new row into the table of the target warehouse utilizing a SQL insert statement PostgreSQL RIGHT join - fetches a complete set of records from the right, with the matching records (depending on the availability) in left. The result is NULL in the left side when no matching will take place.

PostgreSQL LEFT join- fetches a complete set of records from the left, with the matching records (depending on the availability) in right. The result is NULL in the right side when no matching will take place.

The INNER JOIN keyword- selects records that have matching values in both tables. SYNTAX SELECT column_name(s) FROM table 1 INNER JOIN table 2 ON table1.column_name + table2.column_name; The most common processes used for transformation -conversion, clearing the duplicates, standardizing, filtering, sorting, translating and looking up or verifying if the data sources are inconsistent The extraction process must- convert the data into a format suitable for transformation processing. The complexity of the extraction process may vary and it depends on the type and amount of source data....