Function	Description
substring(column,beginInclusive)	Get column.substring(beginInclusive). Output is a STRING.
substring(column,beginInclusive,endExclusive)	Get column.substring(beginInclusive,endExclusive). Output is a STRING.
truncate(column,width)	Truncate column by width. Output type is the same with column. If the column is a STRING, truncate(column,width) will truncate the string to width characters, namely value.substring(0, width). If the column is an INT or LONG, truncate(column,width) will truncate the number with the algorithm v - (((v % W) + W) % W). The redundant compute part is to keep the result always positive. If the column is a DECIMAL, truncate(column,width) will truncate the decimal with the algorithm: let scaled_W = decimal(W, scale(v)), then return v - (v % scaled_W).
cast(value,dataType)	Get a constant value. The output is an atomic type, such as STRING, INT, BOOLEAN, etc.
upper(value)	Convert string column to upper case. The input should be a STRING and the output is a STRING.
lower(value)	Convert string column to lower case. The input should be a STRING and the output is a STRING.
trim(value)	Trim string column. The input should be a STRING and the output is a STRING.