# A .diff()

Description:

Calculate the difference between sequence members of a sequence by removing from the first sub-sequence the members that exist in any of the other sub-sequences.

Syntax:

A .diff()

Note:

Generally sequence A contains multiple sub-sequences. The function calculates the difference between its sequence-type members to ensure that the new sequence doesn’t include any member of the other sub-sequences.

The algorithm is to compute the difference between the first sub-sequence and the second one, then compute the difference between the result and the third sub-sequence, and so on and so forth.

If the sub-sequences are record sequences, compare records in same position through their store addresses. If the addresses are different, the records are different members.

Parameters:

 A A sequence whose members are sequences

Return value:

A new sequence created by performing difference operations on A’s first sub-sequence and the other sub-sequences.

Example:

 A 1 =[[1,2,3,4,5],[3,7,8]].diff() [1,2,4,5] 2 =[[1,2,3],[3,2],1].diff() [] 3 =[[1,2,2,3],2].diff() [1,2,3] remove only one of the duplicate members 4 =demo.query("select top 2 * from EMPLOYEE") 5 =demo.query("select top 1 * from EMPLOYEE") 6 =[A4,A5].diff() Since A4 and A5 come from different table sequences and have different store addresses, so the same records are regarded as different members

Related functions:

A.xunion()