What does the term Tuple Mean in Relational Databases

Question

Please explain what is meant by tuples in sql Thanks

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Tuple is used to refer to a row in a relational database model  But tuple has little bit difference with row

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Whatever its use in mathematics  a tuple in RDBMS is commonly considered to be a row in a table or result set   In an RDBMS a tuple is unordered  A  tuple in an MDDBMS is the instance of data in a cell with its associated dimension instances  members    What is the tuple in a column family data store

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row from a database table

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tuple   1 record  n-tuple   ordered list of  n  records  Elmasri Navathe book  page 198 3rd edition    record   either ordered or unordered

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It s a shortened  N-tuple   like in quadruple  quintuple etc    It s a row of a rowset taken as a whole   If you issue   SELECT  col1  col2 FROM    mytable     whole result will be a ROWSET  and each pair of col1  col2 will be a tuple   Some databases can work with a tuple as a whole   Like  you can do this   SELECT  col1  col2 FROM    mytable WHERE    col1  col2                      SELECT  col3  col4         FROM    othertable               which checks that a whole tuple from one rowset matches a whole tuple from another rowset

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A tuple is used to define a slice of data from a cube  it is composed of an ordered collection of one member from one or more dimensions  A tuple is used to identify specific sections of multidimensional data from a cube  a tuple composed of one member from each dimension in a cube completely describes a cell value

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In relational databases  tables are relations  in mathematical meaning   Relations are sets of tuples  Thus table row in relational database is tuple in relation   Wiki on relations      In mathematics  more specifically  in   set theory and logic   a relation is a   property that assigns truth values to   combinations  k-tuples  of k   individuals  Typically  the property   describes a possible connection   between the components of a k-tuple    For a given set of k-tuples  a truth   value is assigned to each k-tuple   according to whether the property does   or does not hold

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As I understand it a table has a set K of keys and a typing function T with domain K  A row  or  tuple   of the table is a function r with domain K such that r k  is an element of T k  for each key k  So the terminology is misleading in that a  tuple  is really more like an associative array

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Tuples are known values which is used to relate the table in relational DB

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Most of the answers here are on the right track   However  a row is not a tuple   Tuples  are unordered sets of known values with names   Thus  the following tuples are the same thing  I m using an imaginary tuple syntax since a relational tuple is largely a theoretical construct     x 1  y 2  z 3   z 3  y 2  x 1   y 2  z 3  x 1       assuming of course that x  y  and z are all integers   Also note that there is no such thing as a  duplicate  tuple   Thus  not only are the above equal  they re the same thing   Lastly  tuples can only contain known values  thus  no nulls    A row   is an ordered set of known or unknown values with names  although they may be omitted    Therefore  the following comparisons return false in SQL    1  2  3     3  2  1   3  1  2     2  1  3    Note that there are ways to  fake it  though   For example  consider this INSERT statement   INSERT INTO point VALUES  1  2  3    Assuming that x is first  y is second  and z is third  this query may be rewritten like this   INSERT INTO point  x  y  z  VALUES  1  2  3    Or this   INSERT INTO point  y  z  x  VALUES  2  3  1       but all we re really doing is changing the ordering rather than removing it   And also note that there may be unknown values as well   Thus  you may have rows with unknown values    1  2  NULL     1  2  NULL       but note that this comparison will always yield UNKNOWN   After all  how can you know whether two unknown values are equal   And lastly  rows may be duplicated   In other words   1  2  and  1  2  may compare to be equal  but that doesn t necessarily mean that they re the same thing   If this is a subject that interests you  I d highly recommend reading SQL and Relational Theory  How to Write Accurate SQL Code by CJ Date     Note that I m talking about tuples as they exist in the relational model  which is a bit different from mathematics in general     And just in case you re wondering  just about everything in SQL is a row or table   Therefore   1  2  is a row  while VALUES  1  2  is a table  with one row    UPDATE   I ve expanded a little bit on this answer in a blog post here

[sql] What does the term "Tuple" Mean in Relational Databases?

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