SQL and Indexes
Basic I/O Required by SQL DML Requests
The five basic SQL data manipulation language statements, SELECT, INSERT, DELETE, UPDATE, and MERGE, can all use available indexing and partitioning to access and manipulate table rows. Alternatively, the Optimizer applies a full‑table scan if that is more efficient or if there is no applicable index for the request.
The following table summarizes the I/O types required by these four statements.
|
Statement |
Types of I/O Required |
|
SELECT |
Read |
|
INSERT |
Read and Write |
|
DELETE |
|
|
UPDATE |
|
|
MERGE |