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Posted on 2015-01-14
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Last Modified: 2015-01-20
What is the meaning of this. What is happening here


insert into myobjects select * from myobjects;
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Question by:jeevan mathew
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slightwv (䄆 Netminder) earned 500 total points
ID: 40549416
You are creating two of every row in myobjects.

In other words: duplicating the data.

You are inserting into one table the results of a select.  In this case, the same table.
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by:sdstuber
ID: 40549421
that is effectively doubling your data.

"select * from myobjects" returns all rows and columns in the myobjects table.

"insert into myobjects" takes the result of the select statement and inserts all of those results into the table


note - if you have unique constraints or indexes on the table then it's likely the insert will fail because of duplicates on every row
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Expert Comment

by:FarWest
ID: 40549427
if you are suspicious that it will go for infinite loop, no it will not,
The SQL Processor will fetch all rows before insert and then it will insert those rows
if data is large temp tables are used
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Author Closing Comment

by:jeevan mathew
ID: 40560887
Thank you.
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