SQL 语句参数解析：四个问号的含义

SELECT * FROM ( SELECT x.C_VILID, x.C_VILNAME, sum(x.m9) as m9_x, sum(x.m1) as m1_x, sum(x.m2) as m2_x, sum(x.m3) as m3_x, sum(x.m4) as m4_x, sum(x.m5) as m5_x, sum(x.m6) as m6_x, sum(x.m7) as m7_x, sum(x.m8) as m8_x, sum(if(x.C_PROJECTSTATUS=1,1,0)) as finish, sum(if(x.C_PROJECTSTATUS=0,1,0)) as nofinish from db_twenty.t_projectreports x where x.C_TOWID = ? and x.R_STATEMENT_ID = ? and x.C_DELETED = 0 GROUP BY x.C_VILID ) x LEFT join ( SELECT x.C_VILID as C_PLACEID, sum(x.m9) as m9_y, sum(x.m1) as m1_y, sum(x.m2) as m2_y, sum(x.m3) as m3_y, sum(x.m4) as m4_y, sum(x.m5) as m5_y, sum(x.m6) as m6_y, sum(x.m7) as m7_y, sum(x.m8) as m8_y from db_twenty.t_projectreports x where x.C_TOWID = ? and x.C_ANNUAL100+x.C_PERIOD <= ? and x.C_DELETED = 0 GROUP BY x.C_VILID ) y on(x.C_VILID = y.C_PLACEID) 在以上的SQL语句中，有四个问号（?）被用作参数占位符，表示在执行SQL语句时需要传入具体的值。这四个问号分别表示参数的位置如下： 1. 第一个问号（?）表示第一个参数，用于替换x.C_TOWID的值。 2. 第二个问号（?）表示第二个参数，用于替换x.R_STATEMENT_ID的值。 3. 第三个问号（?）表示第三个参数，用于替换y.C_TOWID的值。 4. 第四个问号（?）表示第四个参数，用于替换y.C_ANNUAL100+x.C_PERIOD的值。