神通数据库下 一下SQL怎么写 SELECT @ROWNUM := @ROWNUM + 1 AS TEMPRANK, @INCRNUM := CASE WHEN @ROWTOTAL = OBJ.YLCOUNT + 1 THEN @INCRNUM WHEN @ROWTOTAL := OBJ.YLCOUNT + 1 THEN @ROWNUM END AS FILERANK, OBJ.* FROM ( SELECT DOCINFO.TITLE, DOCINFO.DOC_ID AS DOCID, DOCINFO.DOC_TYPE AS DOCTYPE, U.USER_NAME AS AUTHORNAME, CONCAT( U.USER_NAME, '/', CASE WHEN O.SHORT_NAME = '' THEN '无' ELSE O.SHORT_NAME END ) AS USERNAME, IFNULL( DOCINFO.DOWNLOAD_NUM, 0 ) AS YLCOUNT FROM DOC_INFO DOCINFO, SYS_USERS U, SYS_ORGAN O, sys_stru WHERE DOCINFO.VALID_FLAG = '1' AND IFNULL( DOCINFO.DOWNLOAD_NUM, 0 ) != 0 AND U.USER_ID = DOCINFO.AUTHOR_ID AND sys_stru.STRU_ID = U.DEPARTMENT_ID AND O.ORGAN_ID = sys_stru.ORGAN_ID GROUP BY DOCINFO.DOC_ID, U.USER_NAME ORDER BY DOCINFO.DOWNLOAD_NUM DESC, DOCINFO.TITLE DESC ) OBJ, ( SELECT @ROWNUM := 0, @ROWTOTAL := NULL, @INCRNUM := 0 ) R

这是一个比较复杂的 SQL 语句，主要是用于对文档信息表进行排序和排名操作，并且使用了 MySQL 中的用户变量。

下面是这个 SQL 语句的详细解释：

SELECT
    @ROWNUM := @ROWNUM + 1 AS TEMPRANK, -- 对每一行进行排名，使用用户变量 @ROWNUM
    @INCRNUM := CASE
        WHEN @ROWTOTAL = OBJ.YLCOUNT + 1 THEN @INCRNUM -- 如果当前行的下载数量和上一行一样，则排名也相同
        WHEN @ROWTOTAL := OBJ.YLCOUNT + 1 THEN @ROWNUM -- 否则，将 @ROWNUM 赋值给 @INCRNUM
    END AS FILERANK, -- 最终排名结果
    OBJ.* -- 选择所有表格列
FROM (
    SELECT 
        DOCINFO.TITLE, -- 文档标题
        DOCINFO.DOC_ID AS DOCID, -- 文档 ID
        DOCINFO.DOC_TYPE AS DOCTYPE, -- 文档类型
        U.USER_NAME AS AUTHORNAME, -- 作者姓名
        CONCAT(U.USER_NAME, '/', CASE WHEN O.SHORT_NAME = '' THEN '无' ELSE O.SHORT_NAME END) AS USERNAME, -- 用户名
        IFNULL(DOCINFO.DOWNLOAD_NUM, 0) AS YLCOUNT -- 下载数量
    FROM 
        DOC_INFO DOCINFO, -- 文档信息表
        SYS_USERS U, -- 用户表
        SYS_ORGAN O, -- 组织表
        sys_stru -- 组织结构表
    WHERE 
        DOCINFO.VALID_FLAG = '1' -- 有效标志
        AND IFNULL(DOCINFO.DOWNLOAD_NUM, 0) != 0 -- 下载数量不为零
        AND U.USER_ID = DOCINFO.AUTHOR_ID -- 用户 ID 对应的作者 ID
        AND sys_stru.STRU_ID = U.DEPARTMENT_ID -- 用户所在部门对应的组织结构 ID
        AND O.ORGAN_ID = sys_stru.ORGAN_ID -- 组织表中的组织 ID 对应的组织结构 ID
    GROUP BY
        DOCINFO.DOC_ID, -- 文档 ID
        U.USER_NAME -- 用户名
    ORDER BY
        DOCINFO.DOWNLOAD_NUM DESC, -- 下载数量降序排列
        DOCINFO.TITLE DESC -- 标题降序排列
) OBJ, (SELECT @ROWNUM := 0, @ROWTOTAL := NULL, @INCRNUM := 0) R -- 初始化用户变量

这个 SQL 语句的作用是将文档信息表中的文档按照下载数量和标题进行降序排列，并且对每个文档进行排名，最终返回排序后的结果集。