I'm not that familiar with MySQL, so I can't say how it works. However, I can talk to SQL Server. The key here is that first column. There are two...

The statistics went out of date and need to be updated. As was already stated, the data changed, the statistics changed, a new threshold was reached, and when the plan...

Total agreement with Jeff & Brian.

I will say though, to a degree, and there are hundreds of caveats to this, what makes a good index in one RDBMS, roughly translates...

Just and idea for the future. To be helpful to others, go ahead and leave the question up, but supply the answer too. That way, the next person who hits...

Is this person in way over their head?  It seems like he was dumped in a closet and given orders to find out everything.  He's been pretty prolific with...

All you can do with the information you have is infer the schedule and plan. That's it. You can't know what the intent is. You can't know what the Service...

You're approaching it all in the perfect manner. 1) find solutions to the problems at hand 2) use those solutions as a way to improve your skills.

Keep going. Don't hesitate...

Oh, and if you have specific questions for follow up, don't hesitate to open another thread if necessary. More people will see the question that way. However, as much as...

Hello, and welcome to the party!

There's a lot to unpack there, but I'll try to help a little. These are the questions I spotted.

1. Are data warehouses older technology?

At this...

MY HERO!!!!

Yes, as long as they're actually taking SQL Server backups. There are some...

Thank you Grant, and all, for your advises.

What I also heard is that we need to collect a database workload from production and apply it on our testing environment...

I know it's not free, but it's good. I'd strongly suggest you be ready to invest in your own career and skills. Books are a pretty minor investment in the...

Testing, testing, testing, then test some more.

One thing many people don't know about when upgrading SQL Server using the modern versions (2016+), is Query Store. This is a major tool...

You can look at the backup tables in MSDB, backupset. There's a lot of information there on the type of backup, when it occurred, if it was successful, etc....