These are two simple stock quotes tables that contain a symbol and a close
amount.
Explain
Select Monday.Symbol, Friday.Close, Monday.Close
From Monday Force Index(Symbol) Inner Join Friday Force Index(Symbol) ON
Monday.Symbol = Friday.Symbol
Symbol is a VarChar(20) in both tables.
There is an index on Symbol for both of these table.
The resultant Explain shows that
+----------+------+-----------------+------------+---------+----------------
---+-----------+-------------+
| table | type | possible_keys | key | key_len | ref
| rows | Extra |
+----------+------+-----------------+------------+---------+----------------
---+-----------+-------------+
| Monday | All | Symbol | [Null] | [Null] |
[Null] | 60134 | |
+----------+------+-----------------+------------+---------+----------------
---+-----------+-------------+
| Friday | ref | Symbol | Symbol | 21 |
Monday.Symbol | 1 | where used |
+----------+------+-----------------+------------+---------+----------------
---+-----------+-------------+
Why aren't both using the Symbol key?
Why isn't the Force Index working?
TIA
Dan
