A little warning before using these queries. They may or may not give the true accurate number of records in the tables. These examples illustrate extracting the number of records from the data dictionaries of the databases. This is dependent on background processes being run to gather this information. These background processes run from time to time, anything from a few minutes to many tens of minutes. So, these results are good indication of the number of records in each table.
Click through for examples in Oracle, MySQL, Postgres, SQL Server, and Snowflake. Though the SQL Server one does need a GROUP BY clause because it’s a sum of the partitions’ rows.