NEW YORK -- Microsoft Corp. and Ashton-Tate Corp., two of the biggest names in personal-computer software, said last week they will join forces to sell a piece of software that analysts say could challenge IBM.

The program, SQL Server, will allow users of personal computers that are tied into networks to share a base of information that is stored somewhere in the network.

International Business Machines Corp.'s new line of personal computers, Personal System-2, will have similar capabilities when IBM begins selling the "extended edition" of its new operating system, or internal software.

SQL Server is based on a program licensed from Sybase Inc., a small, closely held software company based in Berkeley, Calif., in which Apple Computer Inc. has a minority interest.

The software includes enhancements from both Microsoft, of Redmond, Wash., and Ashton-Tate, of Torrance, Calif.

Microsoft is the world's biggest independent seller of personal computer software. Ashton-Tate ranks third, behind Lotus Development Corp. The two companies are traditionally rivals.

Ashton-Tate is hoping the combination with SQL Server will boost sales of its dBase family, the best-selling line of data base programs for PC's. However, SQL Server can also be bought separately from dBase, the companies said.

SQL Server will allow networked PCs to do jobs that used to be possible only with minicomputers or mainframes, such as large-scale accounting, inventory management and document storage and retrieval, the companies said.

The program will be available from Ashton-Tate in the second half of 1988, the companies said. Microsoft will license the product to hardware manufacturers.

IBM's competitors in personal computers are trying to show that all the functions provided by IBM's new PS-2 line will also be available on personal computers that use the older standard.

The introduction of SQL Server is a step in that direction. A previous step was Microsoft's announcement last year of software developed with 3Com Corp. that manages communications among personal computers in a network.

Microsoft and Ashton-Tate said they will encourage other companies to write programs that take advantage of SQL Server's features.

In addition to challenging IBM's software, SQL Server is also intended to compete with other companies that sell data base programs, such as Oracle Systems Corp. and Borland International Inc.

Although Microsoft is a rival of IBM, it worked closely with IBM on developing the PS-2 operating system.