When a column will be used in more than one type of query, more than one column index type might be appropriate.
Table 6-6 shows which index types make good combinations.
Index to Add |
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Existing Index |
HG |
HNG |
LF |
CMPa |
WD |
DATE, TIME, or DTTM |
HG |
- |
1 |
2 |
1 |
1 |
1 |
HNG |
1 |
- |
1 |
1 |
2 |
2 |
LF |
2 |
1 |
- |
1 |
2 |
1 |
1 = A reasonable combination 2 = Combination not recommended a. A CMP index applies to a pair of columns. Each of those columns always has at least one other index. |
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