mysql5.7的row_number函数

在MySQL 5.7版本中，没有内置的ROW_NUMBER函数的写法。如果你需要实现类似ROW_NUMBER功能，可以使用变量和子查询来实现。以下是一种实现方式：

CREATE TABLE TZ_DIAG_STAND 
SELECT * 
FROM (
    SELECT 
        @RN := CASE WHEN @DIAGNOSIS_NAME = DIAGNOSIS_NAME THEN @RN + 1 ELSE 1 END AS RN,
        @DIAGNOSIS_NAME := DIAGNOSIS_NAME AS DIAG_NAME, 
        MASTER_ID, 
        NUM 
    FROM (
        SELECT 
            T1.DIAGNOSIS_NAME, 
            MASTER_ID, 
            COUNT(1) NUM 
        FROM (
            SELECT MASTER_ID, DIAGNOSIS_NAME 
            FROM ICD_10 
            WHERE MASTER_ID IS NOT NULL AND DIAGNOSIS_NAME = '妊娠合并肠炎'
        ) T1 
        GROUP BY T1.DIAGNOSIS_NAME, MASTER_ID 
        ORDER BY DIAGNOSIS_NAME, NUM DESC
    ) A, 
    (SELECT @RN := 0, @DIAGNOSIS_NAME := 0) B
) A 
WHERE RN = 1;

这个查询使用了变量@RN和@DIAGNOSIS_NAME来模拟ROW_NUMBER函数的功能，并在最外层的WHERE子句中选择RN等于1的记录。这样就可以获得诊断编码出现最多的记录。请注意，这只是一种实现方式，具体的查询语句可能会根据实际情况有所调整。<span class="em">1</span><span class="em">2</span><span class="em">3</span>
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