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Tag Archives: SQL
Best Explanation on SQL joins in Oracle
SQL*Plus Enhancements
PDB Support
SQL*Plus includes support for the multitenant architecture.
The SHOW
command displays information about PDBs.
SQL> SHOW CON_ID CON_ID ------------------------------ 1 SQL> SHOW CON_NAME CON_NAME ------------------------------ CDB$ROOT SQL> SHOW PDBS CON_ID CON_NAME OPEN MODE RESTRICTED ---------- ------------------------------ ---------- ---------- 2 PDB$SEED READ ONLY NO 3 PDB1 READ WRITE NO
Command History
Before we can use the HISTORY
command we have to make sure it is turned on. In the example below we attempt to use the HISTORY
command with no options and we are told the HISTORY
command is not enabled, so we enable it as instructed. Continue reading SQL*Plus Enhancements
Mark data deleted or In-Database Archiving
Rather than deleting data, some applications have a concept of “mark for delete”, so the data remains present in the table, but is not visible to the application. This is usually achieved by doing the following.
- Add an extra column to the relevant tables that holds a flag to indicate the data is deleted.
- Add an extra predicate to every statement that checks the deleted status, like “
WHERE deleted = 'N'
“, to exclude the deleted rows from the SQL and then create a view on that table to display only “active” records.
In-Database Archiving is a feature added to Oracle Database 12c to allow this type of “mark for delete” functionality out-of-the-box, with fewer changes to the existing application code.
Oracle for Absolute Beginners
Hi to all.
I found a nice series of articles for beginners. I highly suggest to review them if you are new to Oracle: