HDFC Bank on Thursday became the second most valuable company by market capitalisation, overtaking IT behemoth Tata Consultancy Services.At the close of trade, HDFC Bank, which recently completed the merger of its mortgage financier parent HDFC into itself, commanded a market capitalisation (mcap) of Rs 12,72,718.60 crore, which was Rs 5,826.95 crore more than TCS’ Rs 12,66,891.65 crore valuation on the BSE.