SQL/MX 2.x Reference Manual (H06.04+)

SQL/MX Statements
HP NonStop SQL/MX Reference Manual—540440-003
2-189
SELECT Statement
READ UNCOMMITTED
specifies that any data accessed need not be from committed rows. You can
specify the SQL/MP extension BROWSE instead of READ UNCOMMITTED.
READ COMMITTED
specifies that any data accessed must be from committed rows.
SERIALIZABLE | REPEATABLE READ
specifies that the SELECT statement and any concurrent process (accessing
the same data) execute as if the statement and the other process had run
serially rather than concurrently.
SKIP CONFLICT
enables transactions to skip rows locked in a conflicting mode by another
transaction. SKIP CONFLICT cannot be used in a SET TRANSACTION
statement.
STABLE
specifies that the row being accessed is locked while it is processed, but
concurrent use of the database is allowed.
The default access option is the isolation level of the containing transaction, which
is determined according to the rules specified in Isolation Level on page 10-45.
IN {SHARE | EXCLUSIVE} MODE
specifies that either SHARE or EXCLUSIVE locks be used when accessing data
specified by a SELECT statement or by a table reference in the FROM clause
derived from the evaluation of a query expression that is a SELECT statement, and
when accessing the index, if any, through which the table accesses occur.
UNION [ALL] select-stmt
specifies a set UNION operation between the result table of a SELECT statement
and the result table of another SELECT statement.
The result of the UNION operation is a table that consists of rows belonging to
either of the two contributing tables. If you specify UNION ALL, the table contains
all the rows retrieved by each SELECT statement. Otherwise, duplicate rows are
removed.
The select lists in the two SELECT statements of a UNION operation must have
the same number of columns, and columns in corresponding positions within the
lists must have compatible data types. The select lists must not be preceded by
[ANY N] or [FIRST N].
The number of columns in the result table of the UNION operation is the same as
the number of columns in each select list. The column names in the result table of