merge

合并MERGE

LEFT JOIN

select t.* from table1 left join table2 s on t.class_id = s.class_id

df3 = pd.merge(df, df2, how='left', on=['CLASS_ID'])
print(df3)

RIGHT JOIN

select t.* from table1 right join table2 s on t.class_id = s.class_id

df4 = pd.merge(df, df2, how='right', left_on=[
               'CLASS_ID'], right_on=['CLASS_ID'])
print(df4)

INNER JOIN

select t.* from table1 inner join table2 s on t.class_id = s.class_id

df4 = pd.merge(df, df2, how='inner', left_on=[
               'CLASS_ID'], right_on=['CLASS_ID'])
print(df4)

OUTER JOIN

select t.* from table1 full outer join table2 s on t.class_id = s.class_id

df6 = pd.merge(df, df2, how='outer', left_on=[
               'CLASS_ID'], right_on=['CLASS_ID'])
print(df6)