SQL-complete-tutorial

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-- When indexes are ignored
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EXPLAIN SELECT customer_id FROM customers
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WHERE state = 'CA' OR points > 1000;
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-- to speed up this index, we use UNION and 
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-- create an index on the customers' column points;
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CREATE INDEX idx_points ON customers (points);
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	EXPLAIN 
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		SELECT customer_id FROM customers
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		WHERE state = 'CA' 
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		UNION 
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		SELECT customer_id FROM customers
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		WHERE points > 1000;
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EXPLAIN SELECT customer_id FROM customers
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WHERE points + 10 > 2010;
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-- to speed up the index for this query, we isolate our columns like this:
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EXPLAIN SELECT customer_id FROM customers
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WHERE points > 2000;