Example: DELETE Statement 
In the ADDRESS table, the CITY column is defined as the primary key.
A user enters a DELETE statement in order to delete from the table the entry Apach for the primary key field CITY.
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1. The database system deletes the data record and its position entry from the corresponding leaf page.
This leaves gaps in the leaf page.
2. The database system closes these gaps and then updates the address information in the position list of the leaf page.
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