Sql 如何将行值显示为列？

我有这张桌子：

FIELD_CODE  PY_DATIME   PARAM_NAME  PARAM_VAL


F262/034    29-JAN-2021 IRRIGATION_AMOUNT   0
F262/034    29-JAN-2021 MAX_TS_20   250
F262/034    29-JAN-2021 MAX_TS_40   168
F262/034    29-JAN-2021 ET  1.616806
F262/034    30-JAN-2021 MDS 25
F262/034    30-JAN-2021 GROWTH  -8.333333
F262/034    30-JAN-2021 PLANT_STATUS    90
F262/034    30-JAN-2021 IRRIGATION_AMOUNT   0
F262/034    30-JAN-2021 MAX_TS_20   81
F262/034    30-JAN-2021 MAX_TS_40   83
F262/034    30-JAN-2021 ET  1.1099839
F262/034    31-JAN-2021 MDS 56.666668
F262/034    31-JAN-2021 GROWTH  18.333334
F262/034    31-JAN-2021 PLANT_STATUS    70
F262/034    31-JAN-2021 IRRIGATION_AMOUNT   0
F262/034    31-JAN-2021 MAX_TS_20   114
F262/034    31-JAN-2021 MAX_TS_40   95
F262/034    31-JAN-2021 ET  2.2792487

我想这样显示数据：

FIELD_CODE PY_DATIME MDS GROWTH  PLANT_STATUS    IRRIGATION_AMOUNT   MAX_TS_20   MAX_TS_40 ET

我需要从PARAM_NAME列中获取值，并使它们成为列。 并将参数值作为值。 但仅显示一次PY_DATIME和字段代码

表的主键是（字段代码、PY数据时间、参数名称）

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谢谢。

您可以为此使用条件聚合——假设您事先知道所需的列：

select field_code, py_datetime,
       max(case when param_name = 'MDS' then param_val end) as mds,
       max(case when param_name = 'GROWTH' then param_val end) as GROWTH,
       max(case when param_name = 'PLANT_STATUS' then param_val end) as PLANT_STATUS,
       max(case when param_name = 'IRRIGATION_AMOUNT' then param_val end) as IRRIGATION_AMOUNT,
       max(case when param_name = 'MAX_TS_20' then param_val end) as MAX_TS_20,
       max(case when param_name = 'MAX_TS_40' then param_val end) as MAX_TS_40,
       max(case when param_name = 'ET' then param_val end) as ET
from t
group by field_code, py_datetime;

---

您可以为此使用条件聚合——假设您事先知道所需的列：

select field_code, py_datetime,
       max(case when param_name = 'MDS' then param_val end) as mds,
       max(case when param_name = 'GROWTH' then param_val end) as GROWTH,
       max(case when param_name = 'PLANT_STATUS' then param_val end) as PLANT_STATUS,
       max(case when param_name = 'IRRIGATION_AMOUNT' then param_val end) as IRRIGATION_AMOUNT,
       max(case when param_name = 'MAX_TS_20' then param_val end) as MAX_TS_20,
       max(case when param_name = 'MAX_TS_40' then param_val end) as MAX_TS_40,
       max(case when param_name = 'ET' then param_val end) as ET
from t
group by field_code, py_datetime;

---

检查

PIVOT

子句，它应该允许您实现您想要的。检查

PIVOT

子句，它应该允许您实现您想要的。