如何从 YYYY-MM-DD HH:MI:SS 转换 DATETIME。 使用 SQL 到 YYYY-MM

Question

Using a platform that supports Oracle, SQL Server, IBM DB2, MySQL, Sybase, Informix, PostgreSQL and ANSI SQL dialects.

I need to be able to group customer sales by year and month. The desired date format is YYYY-MM eg 2019-06. The current format is YYYY-MM-DD HH:MI:SS.

Below is what I have so far. I have tried many different things but unable to get to work as desired.

SELECT DISTINCT "Customer Name",
ROUND(SUM("Price Ex"), 2) AS 'Sales'
FROM  "ZOHO-0006 Invoice Lines" 
GROUP BY "Customer Name"

Answer 1

If the data type is a string, you can use:

SELECT LEFT(datecol, 7) as yyyymm, ROUND(SUM("Price Ex"), 2) AS Sales
FROM  "ZOHO-0006 Invoice Lines" 
GROUP BY LEFT(datecol, 7);

If the value is stored as a date/time data type, use date functions, such as:

SELECT YEAR(datecol), MONTH(datecol), ROUND(SUM("Price Ex"), 2) AS Sales
FROM  "ZOHO-0006 Invoice Lines" 
GROUP BY YEAR(datecol), MONTH(datecol);

To get the values in one column, you can use format() :

SELECT FORMAT(datecol, '%Y-%m') as yyyymm

Or extract() :

SELECT EXTRACT(year_month from datecol) as yyyymm

Answer 2

If datatype of datecol is timestamp, you can try this:

SELECT 
    TO_CHAR(datecol,'YYYY-MM'), 
    ROUND(SUM("Price Ex"), 2) AS Sales
FROM "ZOHO-0006 Invoice Lines" 
GROUP BY TO_CHAR(datecol,'YYYY-MM');

Or, if it is stored in text/ varchar2 format:

SELECT 
    TO_CHAR(TO_DATE(datecol,'YYYY-MM-DD HH:MI:SS'),'YYYY-MM'), 
    ROUND(SUM("Price Ex"), 2) AS Sales
FROM "ZOHO-0006 Invoice Lines" 
GROUP BY TO_CHAR(datecol,'YYYY-MM');

Also, you no need to do 'distinct' explicitely. 'Group by' operation takes care of it.