A constant indicating that dirty reads, non-repeatable reads and phantom reads
can occur. This level allows a row changed by one transaction to be read by
another transaction before any changes in that row have been committed
(a "dirty read"). If any of the changes are rolled back, the second
transaction will have retrieved an invalid row.
A constant indicating that dirty reads and non-repeatable reads are
prevented; phantom reads can occur. This level prohibits a transaction
from reading a row with uncommitted changes in it, and it also prohibits
the situation where one transaction reads a row, a second transaction
alters the row, and the first transaction rereads the row, getting
different values the second time (a "non-repeatable read").
A constant indicating that dirty reads, non-repeatable reads and phantom
reads are prevented. This level includes the prohibitions in
ISOLATION_REPEATABLE_READ and further prohibits the situation
where one transaction reads all rows that satisfy a WHERE
condition, a second transaction inserts a row that satisfies that
WHERE condition, and the first transaction rereads for the
same condition, retrieving the additional "phantom" row in the second read.
Returns the enum constant of this type with the specified name.
The string must match exactly an identifier used to declare an
enum constant in this type. (Extraneous whitespace characters are
name - the name of the enum constant to be returned.