It just depends on what you're doing. If you're a DBA you don't have to be the best SQl coder but you'll have to know and understand the ins and outs of database maintenance, security, data modeling, query tuning, and all of that stuff. If you're a SQL developer then you should be able to write complex scripts, build tables, know about data modeling, and how to develop reports, etc. If you're a Data Analyst or something then you should be able to write SQL as well (but I've seen people in data analyst positions that could barely write SQL, SMH, so it just varies).
I'd say if you understand these things below:
1. The clauses...SELECT, FROM, WHERE, GROUP BY, HAVING, ORDER BY
2. Inner Join, Left Join, Right Join
3. Sub Queries
4. Stored Procedures
5. Variables
6. Different Functions
7. Views
8. Unions
9. Aggregates (Count, Sum, Min, Max, etc)
10. Data Types (Integer, decimal, varchar, char, date, timestamp, etc.)
Your're golden and somebody will hire you. And from there, it's pretty much based on self-learning and getting better by expanding that knowledge working on different projects at work.
Appreciate the knowledge. SQL will definitely come in useful