Support Decimal type

[KKould]

Feature Request

TPC-H:

CREATE TABLE lineitem (
    l_orderkey INT,
    l_partkey INT,
    l_suppkey INT,
    l_linenumber INT,
    l_quantity DECIMAL(15,2),
    l_extendedprice DECIMAL(15,2),
    l_discount DECIMAL(15,2),
    l_tax DECIMAL(15,2),
    l_returnflag CHAR(1),
    l_linestatus CHAR(1),
    l_shipdate DATE,
    l_commitdate DATE,
    l_receiptdate DATE,
    l_shipinstruct CHAR(25),
    l_shipmode CHAR(10),
    l_comment VARCHAR(44),
    PRIMARY KEY (l_orderkey, l_linenumber)
);

[KKould]

Tips: Decimal needs to support unary/binary operators