--schday (alter)
CREATE TABLE _schday (
uid INTEGER NOT NULL DEFAULT 0,
sch INTEGER NOT NULL, 
num INTEGER NOT NULL,
wduid1 INTEGER NOT NULL DEFAULT 0,
wduid2 INTEGER NOT NULL DEFAULT 0,
wduid3 INTEGER NOT NULL DEFAULT 0,
wduid4 INTEGER NOT NULL DEFAULT 0,
PRIMARY KEY (sch, num));

INSERT INTO _schday (uid, sch, num, wduid1, wduid2, wduid3, wduid4)
SELECT sd.uid, sd.sch, sd.num, 0, 0, 0, 0 FROM schday AS sd;

UPDATE _schday SET wduid1 = (SELECT wd.uid FROM schday AS sd, wday AS wd WHERE sd.uid = _schday.uid AND sd.wk = wd.wk AND sd.wdnum = wd.num)
WHERE EXISTS (SELECT wd.uid FROM schday AS sd, wday AS wd WHERE sd.uid = _schday.uid AND sd.wk = wd.wk AND sd.wdnum = wd.num);

DROP TABLE schday;

ALTER TABLE _schday RENAME TO schday;
