SQL嵌套查询总结

$sql="SELECT type , sum( yjsl ) as yjsl , sum( yysl ) as yysl, sum( jyrs ) as jyrs, sum( jycs ) as jycs
FROM (
SELECT c.mc AS
TYPE , count( d.lsh ) AS yjsl, 0 AS yysl, 0 AS jyrs, 0 AS jycs
FROM sys_dzxxb AS b, sys_jcb AS c, sys_dzyjb AS d
WHERE b.bm = c.lsh
AND d.dzlsh = b.lsh
GROUP BY c.mc
UNION SELECT c.mc AS
TYPE , 0 AS yjsl, count( e.lsh ) AS yysl, 0 AS jyrs, 0 AS jycs
FROM sys_dzxxb AS b, sys_jcb AS c, sys_dzyy AS e
WHERE b.bm = c.lsh
AND e.dzlsh = b.lsh
GROUP BY c.mc
UNION SELECT c.mc AS
TYPE , 0 AS yjsl, 0 AS yysl, count( DISTINCT e.dzlsh ) AS jyrs, 0 AS jycs
FROM sys_dzxxb AS b, sys_jcb AS c, sys_ltxxb AS e
WHERE b.bm = c.lsh
AND e.dzlsh = b.lsh
GROUP BY c.mc
UNION SELECT c.mc AS
TYPE , 0 AS yjsl, 0 AS yysl, 0 AS jyrs, count( DISTINCT e.lsh ) AS jycs
FROM sys_dzxxb AS b, sys_jcb AS c, sys_ltxxb AS e
WHERE b.bm = c.lsh
AND e.dzlsh = b.lsh
GROUP BY c.mc
) AS temptable
GROUP BY TYPE ";