问题
I have column 'Age' (Varchar) How can I select query and convert it to (float)
Pet_Name Age(varchar)
John 2 years 6 months.
Anne 3 years and 6 months.
output:
Pet_Name Age(float/double)
John 2.5
Anne 3.5
my problem is that the inputs does not follow a specific date/age format and was entered as string.
回答1:
Assuming the age column always has two numbers, I have used REGEXP_SUBSTR function in Redshift to write below answer:
create temp table pets (petname varchar(10), age varchar(20));
insert into pets values ('john','2 years 6 mnths');
insert into pets values ('anne','3 Years and 4 months');
insert into pets values ('buddy','4 yrs and 3 Mnths');
insert into pets values ('tommy','9 Years and 5 mnths');
insert into pets values ('alex','5 YEARS and 12 mnts');
insert into pets values ('bob','0 year and 7 Mnts');
insert into pets values ('danny','10 years 11 mnths');
insert into pets values ('sunny','81 years 10 mnths');
select petname,(REGEXP_SUBSTR(AGE,'[0-9]|[0-9][0-9]',1))::integer+(REGEXP_SUBSTR(AGE,'[0-9]|[0-9][0-9]',3))/12 as age from pets;
+--------------------+
|petname | age |
+--------------------+
|john |2.5000 |
|sunny |81.8333 |
|danny |10.9166 |
|anne |3.3333 |
|alex |6.0000 |
|tommy |9.4166 |
|bob |0.5833 |
|buddy |4.2500 |
+--------------------+
Note: The above answer works only when there are two numbers in the age column.
来源：https://stackoverflow.com/questions/47275801/convert-varchar-to-float-double