 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
• |
EXPLAIN SELECT (continued)
|
|
|
|
– |
Possible keys
|
|
|
|
• |
What MySQL had to choose from
|
|
|
|
– |
Key
|
|
|
|
• |
What it decided to use
|
|
|
|
– |
Key length
|
|
|
|
• |
Length (in bytes) of the longest key
|
|
|
|
– |
Ref
|
|
|
|
• |
Which column it will match with
|
|
|
|
– |
Rows
|
|
|
|
• |
Approximately how many rows must be examined
|