Whenever you have a scalar subquery in Oracle, there are a few different options that Oracle can use for executing the subquery. Oracle can either run the query once for each row returned by the records in the from clause.… Read More
ORA-01031: insufficient privileges
ORA-01031: insufficient privileges is probably my least favorite error, because more often than not, it’s an indication of a people problem, and people problems are oftentimes more difficult to fix than technical problems. Having said that, sometimes people issues can… Read More
ORA-30354: Query Rewrite Not Allowed on SYS Relations
The most common reason people get the ORA-30354: Query Rewrite Not Allowed on SYS Relations error is because they’re trying to create a materialized view on a table that exists in the SYS schema. This is a security feature in… Read More
ORA-65049: Creation of local user or role is not allowed in this container
If you’re getting an ORA-65049 error, you’re probably trying to create a local database user (a local database user is a user without a c## prefix) in the CDB$ROOT container for a multi-tenant database. A few solutions exist: If you’re… Read More
“ORA-00904: invalid identifier” with FORALL Loop
Spent an embarrassingly long period of time on an error with a FORALL loop. Can you see what my error is? Every time I ran the above block of code, I would get the following error: Error report – ORA-06550:… Read More
How to Accidentally “Untune” a Query
Suppose one day that you’re at your desk, when you get a telephone call from someone complaining that a query is running slow. You’re given the following setup: And the query that you’re trying to tune looks like this: If… Read More
Filters in the JOIN Clause vs. WHERE Clause: Does It Matter?
Here’s a question I’ve been asked multiple times from multiple people: “Does it matter I put filters in the join clause vs in the WHERE clause? And if so, which one is better?” Example: vs. So does it matter? Answer:… Read More
When to Use APPROX_COUNT_DISTINCT
Since Oracle 12.1, users have had the ability to use the APPROX_COUNT_DISTINCT() function. This function is supposed to be significantly faster than a COUNT(DISTINCT …). Does it really offer that big of a payout? Let’s see: First, let’s make a… Read More
How to Install Oracle 19c on a DigitalOcean Droplet Without ASM (Easiest Install Ever With Tons of Pictures)
If you don’t already have a DigitalOcean account, you’ll want to use this link here to sign up: https://m.do.co/c/97b9d595c7d3 If you use the special link above to sign up, you will get $100 of credit over a 60-day period. Disclaimer… Read More
Over-The-Fence Tuning
One of the best tips on SQL Tuning I can offer you is this: DO NOT DO OVER-THE-FENCE TUNING. It’s taken me years to finally figure this out. What do I mean by over-the-fence SQL Tuning? It goes like this:… Read More