Each organization have certain expectations from their developers, these expectations depend on the project at hand and the seniority of the developer. Here are some of the topics that cover all developer roles:
0-Build database scheme, tables, procedures and permissions.
1-Index design basics and when to use each type of index.
2-Query performance analysis and tuning - How and what tools/commands to use.
3-SQL and common SQL functions.
4-Database scripting language (T-SQL, PL/SQL) and when to use and when not to use.
5-Primary Keys/Foreign Keys design.
6-At least the first 3 Normal Forms ormalization (pros and cons).
7-Triggers types and when to use and not use.
8-Loading database from files.
9-Database environment parameters that needs to be set and why.
10-Logical database modeling, and some physical database modeling although, DBAs would know about that more. If applying for ETL job, need to know about star schema.
11-Referential Integrity constraint types and their effects.
12-Key design/selection best practices.
13-How to use the database management environment.
14-How to invoke the database commands from console.
15-How to write basic DDL (Create Table, etc.).
16-What is a dead lock and how to avoid it.
17-Views and their usage
18-What is a RDBMS!
There are several references for the above knoweldge, The following were added to address some of the comments:
Index Types - MSDN
Index Types and Query Optimaization
Database Engine Advisor - MSDN
SQL Server Profiler
FYI - See related question: software-developer-interview-question-fair-or-unfair