将 MS SQL 转换为 Snowflake SQL，如何使用子查询返回记录计数

Question

我正在将查询从 MS SQL 转换为 Snowflake SQL，我想知道如何使用子查询（或等效于 Snowflake）来转换记录数。在下面的代码中，“NUM_VISITS”返回每位患者的遭遇次数。

如果我硬编码一个静态数字来代替“NUM_VISITS”，则查询不会出现问题，因此我确信问题在于我如何调用子查询。运行显示的代码时，出现以下错误：

SQL 编译错误：第 15 行的第 20 位语法错误出现意外的“SELECT”。位置 32 处的第 15 行语法错误意外'('。

SELECT
    
    'HB' as "TXN_SOURCE",
    enc.PAT_ID,
    enc.PAT_ENC_CSN_ID,
    enc.contact_date,
    enc.PRIMARY_LOC_ID,
    enc.department_id,
    CASE
        WHEN enc.DEPARTMENT_ID = 1229296 AND txn.PROC_ID = 12255396 THEN 'YES'
        ELSE 'NO'
    END as "KITCHEN_CLASS",
    "NUM_VISITS" = (SELECT COUNT(enc2.contact_date)
                    FROM HI_DB.STG_EPICCLARITY_PHS.PAT_ENC enc2
                    JOIN HI_DB.STG_EPICCLARITY_PHS.HSP_TRANSACTIONS txn2
                        ON enc2.PAT_ENC_CSN_ID = txn2.PAT_ENC_CSN_ID
                    WHERE enc.pat_id = enc2.pat_id
                            enc2.CONTACT_DATE BETWEEN $StartDate AND $EndDate
                            AND txn2.PROC_ID IN (12255387,12255388,12255395,12255396)
                            AND enc2.SERV_AREA_ID = 12288)
             ,
    txn.PROC_ID
    
FROM HI_DB.STG_EPICCLARITY_PHS.PAT_ENC enc
JOIN HI_DB.STG_EPICCLARITY_PHS.HSP_TRANSACTIONS txn
    ON enc.PAT_ENC_CSN_ID = txn.PAT_ENC_CSN_ID

WHERE enc.CONTACT_DATE BETWEEN $StartDate AND $EndDate
AND txn.PROC_ID IN (12255387,12255388,12255395,12255396)
AND enc.SERV_AREA_ID = 12288;

在解决了所指出的语法问题后，我能够通过从 JOIN 调用子查询来使代码正常工作。以下是功能代码：

SELECT
    
    'HB' as "TXN_SOURCE",
    enc.PAT_ID,
    enc.PAT_ENC_CSN_ID,
    enc.contact_date,
    enc.PRIMARY_LOC_ID,
    enc.department_id,
    CASE
        WHEN enc.DEPARTMENT_ID = 1229296 AND txn.PROC_ID = 12255396 THEN 'YES'
        ELSE 'NO'
    END as "KITCHEN_CLASS",
    cnt.COUNT,
    txn.PROC_ID
    
FROM HI_DB.STG_EPICCLARITY_PHS.PAT_ENC enc
JOIN HI_DB.STG_EPICCLARITY_PHS.HSP_TRANSACTIONS txn
    ON enc.PAT_ENC_CSN_ID = txn.PAT_ENC_CSN_ID
LEFT JOIN (SELECT   enc2.PAT_ID,
                    COUNT(enc2.contact_date) as "COUNT"
           FROM HI_DB.STG_EPICCLARITY_PHS.PAT_ENC enc2
           JOIN HI_DB.STG_EPICCLARITY_PHS.HSP_TRANSACTIONS txn2
                ON enc2.PAT_ENC_CSN_ID = txn2.PAT_ENC_CSN_ID
           WHERE enc2.CONTACT_DATE BETWEEN $StartDate AND $EndDate
                AND txn2.PROC_ID IN (12255387,12255388,12255395,12255396)
                AND enc2.SERV_AREA_ID = 12288
          GROUP BY enc2.PAT_ID) as cnt ON enc.PAT_ID = cnt.PAT_ID

WHERE enc.CONTACT_DATE BETWEEN $StartDate AND $EndDate
AND txn.PROC_ID IN (12255387,12255388,12255395,12255396)
AND enc.SERV_AREA_ID = 12288;

Answer 1

这是问题中查询的简化：

SELECT x, 
    1 = (SELECT COUNT(1)
                    FROM (select 1 x)
                    WHERE x = 1
                            x BETWEEN 1 AND 5
                            AND x IN (1)
                            AND x = 1)
             ,
    x 
FROM (select 1 x)

您可以看到显示的查询永远不会运行，因为它至少缺少一个AND。

要修复查询，只需在 BETWEEN 行之前添加一个 AND：

SELECT x, 1=(select 1),
    1 = (SELECT COUNT(1)
                    FROM (select 1 x)
                    WHERE x = 1
                            AND x BETWEEN 1 AND 5
                            AND x IN (1)
                            AND x = 1)
             ,    x   
FROM (select 1 x);