I’m not sure the size of the largest database I’ve created myself, but the largest I’ve used would be an SAP ECC system. Having a quick look, one of the systems I have access to has 28,247 tables (30,857 indexes). This is a slightly older system (ECC 6.0 EhP4) - a more up-to-date system would no doubt have several thousand more tables. Total size of the system in question is roughly 380GB.

Dozens of thousands, though it’s postgresql, which requires separate tables for every partition of a partitioned table. Barring partitions, it’s probably only ten thousand or so. The largest database with that schema that I manage is in the 25TB range.

Only worked at one company, primarily on one app.

There are 156 tables in that app.

Edit: Sorry, I’m new here, didn’t know the formatting would change “156.” to “1.”

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Our wordpress platform (wordpress MU) has north of 46000 tables. It seem that WordPress thought it a sound design decision to have distinct tables for every single blog…

107

46

From the few DBs I have on this machine, 148 is the most tables in any one of them.

It wasn’t my database, but I saw an application once, for a satellite tv provider, that dynamically created a db table (not row) for every single customer. So there were hundreds of thousands of tables in the app.

Can’t say I’ve ever had any projects with hundreds or thousands of tables with different schemata, but one distributed metrics storage system I worked on had a big database sharded across probably 500+ tables worldwide. The first layer of sharding was regional and depended on where clients sent data. The second layer of sharding was a consistent hash ring setup that could be grown pretty much boundlessly. I suspect that same project might still be going, and, unless they changed other parameters, could easily have 10k+ tables now.

I’d be interested to hear someone from Facebook chime in on their mysql usage.