I’ve created a script that monitors a table in a SQL Server database. I’m only interested in one column in the table: TimeStamp. If the maximum (newest) value in TimeStamp is more than 30 minutes ...

constant is a number or a quoted character string (or other special notation) that indicates a fixed value. Constants are also called literals. query-expression is described in query-expression.

I found it interesting that the order of condition values matters in a crate query. Pleaes check following sql. select ymd, h, sum(lrate) from realChanFlow_test where ...

The EXISTS condition is an operator whose right operand is a subquery. The result of an EXISTS condition is true if the subquery resolves to at least one row. The result of a NOT EXISTS condition is ...