Sainsbury enjoyed a stronger second quarter as its online shopping business expanded fast to deliver more than one billion pounds of sales per year.Like-for-like sales grew 2.1% in the 16 weeks to September 28th even against strong comparatives, with total sales accelerating to 5.0% from 3.6% in the first quarter.With total sales up 4.4% for the first half, Chief Executive Justin King boasted that the grocer had continued to outperform the market in what remained a tough retail environment. "We are the only major supermarket to be growing market share," he pointed out. "This comes during a quarter in which we also lapped some of our strongest performance during the Paralympic Games last year."Recent data from Kantar Worldpanel showed Sainsbury's was the only one of the big four UK grocers to gain market share in the quarter, controlling 16.6% of the market compared with 16.4% a year earlier.The FTSE 100 company's own-brand ranges, 'Taste the Difference' and 'by Sainsbury's', continued to grow at over twice the rate of branded goods.King remarked that the online groceries business grew by more than 15% during the quarter, down from 16% in the first quarter, to be worth over £1bn in annual sales.The company also launched a mobile phone offering, in a joint venture with Vodafone."Our convenience business grew 20 per cent year-on-year as customers topped up more frequently during the warm summer weather," he added, pointing to 31 new convenience stores and five supermarkets opened during the period. Looking forward, King said Sainsbury's had seen encouraging signs in its key economic indicators. "By continuing to focus on high quality, unique and innovative own-brand products we are ideally placed to perform well coming into the key Christmas period."