SQL notes-query data appears only once, small data bits are nonzero, delete tables and sequences, ifnull functions

Only one occurrence of each identical data in the Query data table

SELECT DISTINCT (order_no) from Ibsp_record_fee

The data in the Query data table decimal place is not 0

SELECT * FROM Ibsp_pay_record PR where Pr.amount<>round (pr.amount,0)

Or

SELECT * FROM Ibsp_pay_record PR where pr.amount!= cast (pr.amount as Decimal (13,0))

Delete table and ID sequence

TRUNCATE TABLE Ibsp_balance_account_data

(Oracle)

Oracle Query SQL Time formatter function: to_date (' 2017-12-12 ', ' yyyy-mm-dd hh24:mi:ss ')

The use of the MySQL ifnull function in Oracle is: NVL (column, ' Replace field or value ')

Ifnull (column, ' Replace field or value ') Note: When the entire result of the query is empty, the return is empty

Determine if the data field is empty:

Querying for empty fields or non-empty fields (is null and NOT NULL)

SQL notes-query data appears only once, small data bits are nonzero, delete tables and sequences, ifnull functions