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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.