Define a cursor mode
You can specify one of the following cursor modes for
the cursor with the control-flag bit mask.
| Cursor mode | Description | SELECT statement |
|---|---|---|
| Update | Enables you to read and modify the data within the cursor | SELECT...FOR UPDATE |
| Read-only | Enables you to read the data within the cursor; does not allow you to update or delete any row it fetches | SELECT...FOR READ ONLY |
When you execute a prepared SELECT statement with no FOR
UPDATE or FOR READ ONLY clause, the cursor mode you need depends on
whether your database is ANSI-compliant, as follows:
- In a database that is not ANSI compliant, the SELECT statement
specifies a read-only mode by default.
You do not need to specify the FOR READ ONLY keywords in the SELECT statement. The only advantage of specifying the FOR READ ONLY keywords explicitly is for better program documentation. To specify an update mode, you must specify the FOR UPDATE keywords in the SELECT statement.
- In an ANSI-compliant database, the SELECT statement specifies
an update mode by default.
You do not need to specify the FOR UPDATE keywords in the SELECT statement. The only advantage of specifying the FOR UPDATE keywords explicitly is for better program documentation. To specify a read-only mode, you must specify the FOR READ ONLY keywords in the SELECT statement.
By default, both the sequential and scroll cursor types
have a cursor mode of update (also called read/write). The following
table shows the cursor types and cursor modes, with the required bit-mask
values for the control flag.
| Cursor | Control-flag value |
|---|---|
| Update sequential cursor | None (default) |
| Read-only sequential cursor | MI_SEND_READ |
| Update scroll cursor | MI_SEND_SCROLL |
| Read-only scroll cursor | MI_SEND_READ + MI_SEND_SCROLL |