Question

我对以下查询有所了解。我需要创建一个if语句或类似的东西来区分应该将哪个“CASE”添加到我的选择查询中。

If page_type = 'Region' or 'City'将此内容添加到查询中：

( CASE When landing_page like concat('%',path_id,'%') and
(LENGTH(landing_page) - LENGTH(REPLACE(landing_page, '/' ,'')) / LENGTH('/')) = 2
Then 'True' Else 'False' End as 'correct lp' , )

Elseif page_type = 'Item'将此内容添加到查询中：

( CASE When landing_page like concat('%',path_id,'%') and
(LENGTH(landing_page) - LENGTH(REPLACE(landing_page, '/' ,'')) / LENGTH('/')) = 3
Then 'True' Else 'False' End as 'correct lp' , )

Elseif page_type = 'POI (Alle)'将此内容添加到查询中：

( CASE When landing_page like concat('%',path_id,'%') and
(LENGTH(landing_page) - LENGTH(REPLACE(landing_page, '/' ,'')) / LENGTH('/')) = 3 and
'Hotel' NOT IN landing_page
Then 'True' Else 'False' End as 'correct lp' , )

案例查询应根据if结果添加到以下查询中：

 SELECT
  MONTHNAME(k.crawl_date) As 'Month',
  YEAR(k.crawl_date) As 'Year',
  WEEKOFYEAR(k.crawl_date) As 'Week',
  k.landing_page,
  k.pos,
  CASE WHEN k.pos = 0 THEN 'No Rank' WHEN k.pos < 4 THEN 'Top 3' WHEN k.pos < 11 THEN 'Page 1'
       WHEN k.pos < 21 THEN 'Page 2' WHEN k.pos < 31 THEN 'Page 3' WHEN k.pos < 41 THEN 'Page 4'
       WHEN k.pos < 51 THEN 'Page 5' WHEN k.pos < 61 THEN 'Page 6' WHEN k.pos < 71 THEN 'Page 7'
       WHEN k.pos < 81 THEN 'Page 8' WHEN k.pos < 91 THEN 'Page 9' WHEN k.pos < 101 THEN 'Page 10'
       WHEN k.pos < 111 THEN 'Page 11' END as 'Page', 
 k.path_id,
 k.domain,
 x.keyword,
 x.engine_id,
 l.bucket,
 l.page_type,
 l.item_label
FROM
 xovi_stats k
 LEFT JOIN xovi_keywords x ON k.keyword_id = x.id
 LEFT JOIN xovi_labels l ON l.id = x.label_id

Answer 1

您可以像这样嵌套CASE子句：

SELECT
    CASE
        WHEN (page_type IN ('Region', 'City')) THEN
            CASE
                WHEN landing_page LIKE ... THEN 'True'
                ELSE 'False'
            END
        WHEN (page_type = 'Item') THEN
            CASE
                ...
            END
        WHEN (page_type = 'POI (Alle)') THEN
            CASE
                ...
            END
    END AS lp,
    MONTHNAME(k.crawl_date) As 'Month', -- other fields
    ...

或者您也可以按照建议嵌套IF()：

SELECT
    IF ( (page_type IN ('Region', 'City')),
        -- if (page_type IN ('Region', 'City')) then
        CASE
            WHEN landing_page LIKE ... THEN 'True'
            ELSE 'False'
        END,
        -- else
        IF ( (page_type = 'Item'),
            -- if (page_type = 'Item') then
            CASE
                ...
            END,
            -- else
            IF ( page_type = 'POI (Alle)',
                -- if (page_type = 'POI (Alle)') then
                CASE
                    ...
                END,
                -- else
                NULL
            )
        )
    ) AS lp,
    MONTHNAME(k.crawl_date) As 'Month', -- other fields
    ...

偏离主题的说明：

您可以使用简单的CASE替换您的双分支IF()语句：

SELECT CASE
    WHEN landing_page LIKE ... THEN 'True'
    ELSE 'False'
END AS alias ;

-- strictly equivalent to

SELECT IF(
    landing_page LIKE ...,
    'True',
    'False'
) AS alias ;

您可以使用以下内容替换现有的CASE：

CASE
    WHEN k.pos = 0 THEN 'No Rank'
    WHEN k.pos < 4 THEN 'Top 3'
    ELSE CONCAT('Page ', (k.pos -1) DIV 10 +1 )
END AS 'Page'

如果陈述区分哪个＆＃34;案例＆＃34;应该添加查询以选择查询

1 个答案: