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How to apply a conditional constraint

PericlesJan 22 2025

Hello

I have a table that has six columns. If the fourth column is null, then the first three columns, which are not nullable, must be unique, but if the fourth column is not null, then all the four columns must be unique.

Example of allowed cases:

COL1 COL2 COL3 COL4 COL5 COL6

1 1 1 NULL 123 125

1 1 2 NULL 123 125

1 2 1 NULL 123 125

2 1 1 NULL 123 125

1 1 1 1 123 125

Example of not allowed cases

COL1 COL2 COL3 COL4 COL5 COL6

1 1 1 1 123 125

1 1 1 1 123 125 INSERT/UPDATE MUST FAIL

1 2 1 NULL 123 125

1 2 1 NULL 123 125 INSERT/UPDATE MUST FAIL

There is a way to create a constraint that prevent any insertion in the table that do not accomplish these conditions?

Thanks

This post has been answered by Solomon Yakobson on Jan 22 2025
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Comments

MartinBach-Oracle Jan 8 2025

Hi Salomon,

please have a look at this blog post written by @ulrike-schwinn-oracle :

https://blogs.oracle.com/coretec/post/easy-sql-statement-tracking-in23c

I hope this answers your question, if not, please shout!

- Martin

Solomon Yakobson Jan 8 2025

@martinbach-oracle - No, it doesn't answer my question. Article you pointed to shows uses:

SQL> alter system set sql_history_enabled=true scope=both;

And in my post I said “Works fine when enabled on system level”. My question was about

SQL> ALTER SESSION SET SQL_HISTORY_ENABLED = TRUE;

where I showed SQL history was NOT captured even though it should be based on SQL_HISTORY_ENABLED:

Modifiable **ALTER SESSION**, ALTER SYSTEM

SY.

MartinBach-Oracle Jan 8 2025

As per the article I shared the situation is as follows at the moment

  • You must enable SQL history PDB-wide (only a DBA can do that) so there's a certain level of control over the feature
  • Your session has access to the SQL history
  • If you don't want to record anything, set sql_history_enabled to false.

I'm currently assessing if that's intended behaviour (in which case the documentation should be amended) or a feature not working as it should (in which case it needs fixing). The parameter is indeed session-modifyable, but not in the sense you expected.

We'll keep you posted.

- Martin

Solomon Yakobson Jan 8 2025

Do you mean it must be enabled on system level and not on session level and all session can do is disabe it for the session?

SY.

MartinBach-Oracle Jan 14 2025

Yes,

that's correct as of Oracle Database Free 23.6.

- Martin

Solomon Yakobson Jan 14 2025

Thanks Martin, I hope this will be added to 23AI docs soon.

SY.

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Added on Jan 22 2025
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