In this post, we complete the discussion on Teradata and its SQL. We briefly cover the stored procedures SQL. Teradata follows the SQL conventions so these are similar to writing them elsewhere. However they include comprehensive stored procedure language. They are stored in either DATABASE or USER PERM and are invoked using the CALL statement. It may return one or more values to client as parameter. IN, OUT, and INOUT parameters can be used with the stored procedure.
Triggers can similarly be authored. It is an event driven maintenance operation. When a table is modified, the trigger is executed. The original data modification, the trigger and all subsequent triggers are all part of the same transaction. Triggers can be specified as 'FOR EACH STATEMENT' as well as for each data modification.
The hashing functions on Teradata are also very popular. The HASHROW function is used to produce the 32bit binary Row Hash that is stored as part of the data row. The HashRow function can be executed on data column values. From the above answer of 1, it is a great sign that the data is perfectly distributed or even unique.
The HashBucket function is used to produce the 16 bit binary Hash bucket that is used with the hash map to determine the AMP that should store and retrieve the data row. It can return a maximum of just over 1,000,000 unique values. The HashAmp function returns the identification number of the primary AMP for any hash bucket number. The HashBakAmp function returns the identification number of the Fallback AMP for any Hash Bucket number. A great way to see distribution of primary and fallback rows.
The Batch Teradata query tool has been around for some time. It is a report writer and imports and exports data from a Teradata server one row at a time. Queries can be run interactively or in a batch script. After you logon, you can directly execute queries in interactive mode. The WITH and WITH BY commands are available for totaling and sub-totaling. Scripts can be batched and saved in a text file. This concludes our reading of the book on Teradata
Triggers can similarly be authored. It is an event driven maintenance operation. When a table is modified, the trigger is executed. The original data modification, the trigger and all subsequent triggers are all part of the same transaction. Triggers can be specified as 'FOR EACH STATEMENT' as well as for each data modification.
The hashing functions on Teradata are also very popular. The HASHROW function is used to produce the 32bit binary Row Hash that is stored as part of the data row. The HashRow function can be executed on data column values. From the above answer of 1, it is a great sign that the data is perfectly distributed or even unique.
The HashBucket function is used to produce the 16 bit binary Hash bucket that is used with the hash map to determine the AMP that should store and retrieve the data row. It can return a maximum of just over 1,000,000 unique values. The HashAmp function returns the identification number of the primary AMP for any hash bucket number. The HashBakAmp function returns the identification number of the Fallback AMP for any Hash Bucket number. A great way to see distribution of primary and fallback rows.
The Batch Teradata query tool has been around for some time. It is a report writer and imports and exports data from a Teradata server one row at a time. Queries can be run interactively or in a batch script. After you logon, you can directly execute queries in interactive mode. The WITH and WITH BY commands are available for totaling and sub-totaling. Scripts can be batched and saved in a text file. This concludes our reading of the book on Teradata
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