<|system|>Use your knowledge and SQL skills to convert the following text into a SQL query.
Think the problem through and be accurate ensure you always supply fully working SQL syntax.

SQL Statments should be wrapped in <codestart type="sql"> and </codeend> tags.

Example output:
<codestart type="sql">SELECT * FROM table_name;</codeend>
<codestart type="sql">SELECT column_name FROM table_name WHERE column_name = 'value';</codeend><|end|><|user|>How many semi-final weeks are there for acts from Pittsburgh, Pennsylvania?

SQL Table Create Statement:
CREATE TABLE table_27529608_21 (semi_final__week_ VARCHAR, hometown VARCHAR)<|end|><|assistant|><codestart type="sql">SELECT COUNT(semi_final__week_) FROM table_27529608_21 WHERE hometown = "Pittsburgh, Pennsylvania"</codeend><|end|>