MySQL date calculation and format conversion

The following problems are frequently encountered during development:

1. Use MySQL built-in functions to convert the timeline to the corresponding date

Method 1: Use the from_unixtime (unix_timestamp) function,

For example, select from_unixtime ('20140901 ');

Result: 11:51:18

Select from_unixtime ('20140901', '% Y-% m-% D ');

Result:

2. Use MySQL built-in functions to calculate the date

For example, select all orders that meet the requirements of "three hours ago ".

Method 1: Use unix_timestamp () to convert the time to a timeline, which makes it easier to compare

SQL statement:

Select * From 'order' where unix_timestamp (order_time)> (unix_timestamp (now ()-3600*3)

Method 2: to be continued

To be continued ......