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Indexes
LOCK TABLE attempts to lock all indexes of any table it locks. If an index is not available or if
the lock request times out, LOCK TABLE displays a warning and continues to request locks on
other indexes.
Examples of LOCK TABLE
•
Lock a table with an exclusive lock (at a time when few users need access to the database)
to perform a series of updates:
BEGIN WORK;
LOCK TABLE persnl.employee
IN EXCLUSIVE MODE;
UPDATE persnl.employee
SET salary = salary * 1.05
WHERE jobcode <> 100;
COMMIT WORK;
COMMIT WORK automatically unlocks the table when it ends the transaction.
•
Delete all rows of the JOB table that have a job code that is not assigned to any employee:
BEGIN WORK;
--- SQL operation complete.
LOCK TABLE persnl.job
IN EXCLUSIVE MODE;
--- SQL operation complete.
LOCK TABLE persnl.employee
IN SHARE MODE;
--- SQL operation complete.
DELETE FROM persnl.job
WHERE jobcode NOT IN
(SELECT DISTINCT jobcode
FROM persnl.employee);
--- 1 row(s) deleted.
COMMIT WORK;
--- SQL operation complete.
UNLOCK TABLE persnl.job;
--- SQL operation complete.
128
SQL Statements
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