在以下查询中使用 CAST FUNCTION

Question

the thing is to replace whatever observation that hold the number 999.9 as NULL but i dont know the utility of CAST here as i know it helps change the data type but WDSP in the description is STRING

IF(
    wdsp="999.9",
    NULL,
    CAST(wdsp AS Float64)) AS wind_speed,

nothing yet the cast should it come before IF or within IF

Answer 1

The CAST function in being used to convert the wdsp column to a number (specifically FLOAT64 ) instead of returning it as a STRING (which you mention is the declared type). This is likely being some so that whatever is issuing the query can get the aliased column wind_speed as a numerical type so that is can be processed as a number and not a string.