Oracle
1Z0-888 · Question #3
1Z0-888 Question #3: Real Exam Question with Answer & Explanation
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Performance Tuning
Question
Consider:
mysql> EXPLAIN SELECT * FROM City WHERE Name = 'Jacksonville' AND CountryCode = 'USA'\G
*************************** 1. row ***************************
id: 1
select_type: SIMPLE
table: city
type: ref
possible_keys: name_country_index
key: name_country_index
key_len: 13
ref: const, const
rows: 1
Extra: Using where
Which statement best describes the meaning of the value for the key_len column?
Options
- AIt shows how many bytes will be used from each index row.
- BIt shows the number of characters indexed in the key.
- CIt shows the total size of the index row.
- DIt shows how many columns in the index are examined.
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Topics
#EXPLAIN statement#Index optimization#Key length#Query execution