python - 将空日期填充为 NULL sql 查询

Question

我有一个 csv 文件，如下所示:

Dates   Experiment  Experiment_Type RESET_FREQUENCY MEASURE_LENGTH  Value   Date_Integer
2016-09-28  A   FORWARD_Detector    1 Minute    1   0.99994 20160928
            A   FORWARD_Detector    1 Minute    7   0.99959 20160928
2016-09-28  A   FORWARD_Detector    1 Minute    14  0.99917 20160928
2016-09-28  A   FORWARD_Detector    1 Minute    21  0.99876 20160928
            A   FORWARD_Detector    1 Minute    30  0.99823 20160928

我收到的内容如下:

Dates   Experiment  Experiment_Type RESET_FREQUENCY MEASURE_LENGTH  Value   Date_Integer
2016-09-28  A   FORWARD_Detector    1 Minute    1   0.99994 20160928
0000-00-00  A   FORWARD_Detector    1 Minute    7   0.99959 20160928
2016-09-28  A   FORWARD_Detector    1 Minute    14  0.99917 20160928
2016-09-28  A   FORWARD_Detector    1 Minute    21  0.99876 20160928
0000-00-00  A   FORWARD_Detector    1 Minute    30  0.99823 20160928

但我想要的是:

Dates   Experiment  Experiment_Type RESET_FREQUENCY MEASURE_LENGTH  Value   Date_Integer
2016-09-28  A   FORWARD_Detector    1 Minute    1   0.99994 20160928
NULL        A   FORWARD_Detector    1 Minute    7   0.99959 20160928
2016-09-28  A   FORWARD_Detector    1 Minute    14  0.99917 20160928
2016-09-28  A   FORWARD_Detector    1 Minute    21  0.99876 20160928
NULL        A   FORWARD_Detector    1 Minute    30  0.99823 20160928

我的查询如下所示:

exp_data = """LOAD DATA LOCAL INFILE 'C:/Data.csv' IGNORE 
    INTO TABLE interest_rate_curves_bootstrap 
    FIELDS TERMINATED BY ';' 
    LINES TERMINATED BY "\\n" 
    (@var1,Experiment,Experiment_Type,RESET_FREQUENCY,MEASURE_LENGTH    Value,  Date_Integer) 
    set Dates = STR_TO_DATE(@var1, '%d-%b-%y');"""

我尝试了以下方法，但没有成功:

ALTER TABLE experiment_US MODIFY COLUMN experiment_data DATETIME NULL;

然后更新值:

UPDATE experiment_USSET experiment_data= NULL WHERE experiment_data= '0000-00-00';

import sqlalchemy as sqlal

#connection to mysql database
mysql_engine = sqlal.create_engine('mysql+mysqlconnector://xxx@localhost/rates data')


mysql_engine.raw_connection()

metadata = sqlal.MetaData()

experiment_data = sqlal.Table('experiment_data', metadata,
                                             sqlal.Column('Date_String', sqlal.Date(), nullable=True), 
                                             sqlal.Column('Experiment', sqlal.String(3), nullable=True),
                                             sqlal.Column('Experiment_Type', sqlal.String(8), nullable=True),
                                             sqlal.Column('RESET_FREQUENCY', sqlal.String(3), nullable=True),
                                             sqlal.Column('MEASURE_LENGHT', sqlal.Integer(), nullable=True),
                                             sqlal.Column('Value', sqlal.Float(), nullable=True),
                                             sqlal.Column('Date_Integer', sqlal.Integer(), nullable=True)
                                             )

exp_data = """LOAD DATA LOCAL INFILE 'C:/Data.csv' IGNORE INTO TABLE experiment_data FIELDS TERMINATED BY ';' LINES TERMINATED BY "\\n" (@var1,Experiment,Experiment_Type,RESET_FREQUENCY,MEASURE_LENGTH    Value,  Date_Integer) set Dates = STR_TO_DATE(@var1, '%d-%b-%y');"""

mysql_engine.execute(exp_data)

Answer 1

将最后一行更改为:

SET Dates = IF(@var1 = '', NULL, STR_TO_DATE(@var1, '%d-%b-%y'));"""

这会检查 CSV 字段是否为空，然后将 NULL 放入表中，而不是调用 STR_TO_DATE。