Use of functions like Decode, substr, InStr, replace, length, etc. in SQL Server statements 2016.7.10

Decode () corresponds to case-when function

Case CHARINDEX ('/', start_point_name)

When 0 then Start_point_name

else substring (start_point_name,1,charindex ('/', start_point_name)-1)

End

Note: The syntax is different when SQL Server uses case to determine whether it is null

Null should be judged by:

Case when identifier was NULL then Airway_point_name else identifier end,

The simplest way is to use the ISNLL function IsNull (idenfier, Airway_point_name)

No way! IsNull (Idenfier, Airway_point_name) will idenfier shortened, originally 5 characters, replaced only 4 characters, the reason is unknown, it is best not to IsNull

The InStr corresponds to the charindex ('/', start_point_name) function, except that the meaning of the two parameters is reversed and is counted starting from 1.

SUBSTR corresponds to the substring parameter exactly the same, but the length parameter cannot be missing, cannot default to the end, can give only a large enough length value.

The Replace function is exactly the same

The length function corresponds to the Len function

Use of functions like Decode, substr, InStr, replace, length, etc. in SQL Server statements 2016.7.10