Question

我希望以下查询根据specimen.snop_axis的值进行更改，该值可以是“M”或“F”：

SELECT *
FROM specimen,
     topography_index,
     morphology,
     FUNCTION
WHERE SUBSTRING(specimen.topography_index, 2, 2) = topography_index.topography_index_code
  AND morphology.morphology_code = specimen.snop_code
  AND specimen.topography_index = '_ORGAN_'

因此，如果samples.snop_axis == M则添加

AND morphology.morphology_code = specimen.snop_code

否则如果samples.snop_axis == F则添加

AND functions.function_code = specimen.snop_code

更新

我已根据建议将查询更改为：

SELECT * FROM specimen, topography_index, morphology, functions 
WHERE 
SUBSTRING(specimen.topography_index, 2, 2) = topography_index.topography_index_code 
AND 
IF(specimen.snop_axis == 'M', morphology.morphology_code = specimen.snop_code, functions.function_code = specimen.snop_code) 
AND 
specimen.topography_index = '_ORGAN_'

但是我收到了一个错误：

You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '== 'M', morphology.morphology_code = specimen.snop_code, functions.function_code' at line 1

Answer 1

试试这个。

SELECT *
FROM specimen,
     topography_index,
     morphology,
     FUNCTION
WHERE SUBSTRING(specimen.topography_index, 2, 2) = topography_index.topography_index_code
  AND specimen.topography_index = '_ORGAN_'
  AND if(specimen.snop_axis = 'M', morphology.morphology_code = specimen.snop_code, functions.function_code = specimen.snop_code);

Answer 2

你可以简单地使用这样的case语句： -

SELECT * FROM specimen, topography_index, morphology, function WHERE SUBSTRING(specimen.topography_index, 2, 2) = topography_index.topography_index_code 
AND morphology.morphology_code = specimen.snop_code 
AND specimen.topography_index = '_ORGAN_'
AND CASE WHEN specimen.snop_axis = M THEN morphology.morphology_code = specimen.snop_code
ELSE function.function_code = specimen.snop_code END;

这可能会对你有帮助。

Answer 3

您可以使用逻辑操作AND和OR将它们作为条件子句，如下所示：

SELECT *
FROM specimen,
     topography_index,
     morphology,
     FUNCTION
WHERE SUBSTRING(specimen.topography_index, 2, 2) = topography_index.topography_index_code
  AND morphology.morphology_code = specimen.snop_code
  AND specimen.topography_index = '_ORGAN_'
  AND (
    (specimen.snop_axis = 'M' AND morphology.morphology_code = specimen.snop_code)
    OR 
    (specimen.snop_axis = 'F' AND functions.function_code = specimen.snop_code)
);

Answer 4

SELECT *
FROM specimen,
     topography_index,
     morphology,
     FUNCTION
WHERE SUBSTRING(specimen.topography_index, 2, 2) = topography_index.topography_index_code
AND morphology.morphology_code = specimen.snop_code
AND specimen.topography_index = '_ORGAN_'
AND (if(specimen.snop_axis = 'M', 
     morphology.morphology_code = specimen.snop_code, 
     functions.function_code = specimen.snop_code) 
OR if(specimen.snop_axis = 'F',functions.function_code = specimen.snop_code));

MySQL - 根据字段值修改查询

4 个答案: