Salesforce.com has announced a deal to buy big data firm Tableau Software for $15.3 billion, marking the biggest acquisition in the company's history as it looks to offer more data insights to its clients.

Seattle-based Tableau has more than 86,000 customers, including tech heavyweights such as Verizon Communications and Netflix.

As part of the all-stock deal, Tableau shareholders will get 1.103 Salesforce shares, valuing the offer at $177.88 per share, representing a premium of 42% to Tableau's Friday closing price.

Salesforce's deal comes days after Alphabet's Google bought big-data analytics company Looker for $2.6 billion and surpasses the $5.9 billion that the cloud-based software company paid to buy US software maker MuleSoft in 2018. 

Big data analytics is a complex process used to uncover hidden patterns, unknown correlations, market trends and customer preferences that often help companies make better business decisions.

The deal is expected to close in the third quarter, after which Tableau will operate independently, led by chief executive Adam Selipsky and its current leadership team.

"Tableau helps people see and understand data, and Salesforce helps people engage and understand customers," Salesforce co-CEO Marc Benioff said.

The San Francisco-based company said the deal is likely to add up to $400m in its 2020 revenue, but would decrease adjusted profit by about 37 cents to 39 cents per share.

The company said it now expects 2020 adjusted profit in the range of $2.51 per share to $2.53 per share. Analysts were expecting $2.90 per share, according to IBES data from Refinitiv.

Shares of Tableau jumped 35% to $169.50, while those of Salesforce fell 5% to $156.43 in pre-market trading.