SQL multiple columns in IN clause

Question

If we need to query a table based on some set of values for a given column  we can simply use the IN clause    But if query need to be performed based on multiple columns  we could not use IN clause grepped in SO threads     From other SO threads  we can circumvent this problem using joins or exists clause etc  But they all work if both main table and search data are in the database    E g User table  firstName  lastName  City   Given a list of  firstname  lastName  tuples  I need to get the cities    I can think of following solutions    1  Construct a select query like    SELECT city from user where  firstName x and lastName y  or  firstName a and lastName b  or         2  Upload all firstName  lastName values into a staging table and perform a join between  user  table and the new staging table    Are there any options for solving this problem and what is the preferred of solving this problem in general

User · Answer

Determine whether the list of names is different with each query or reused. If it is reused, it belongs to the database.

Even if it is unique with each query, it may be useful to load it to a temporary table (#table syntax) for performance reasons - in that case you will be able to avoid recompilation of a complex query.

If the maximum number of names is fixed, you should use a parametrized query.

However, if none of the above cases applies, I would go with inlining the names in the query as in your approach #1.

User · Answer

It often ends up being easier to load your data into the database  even if it is only to run a quick query   Hard-coded data seems quick to enter  but it quickly becomes a pain if you start having to make changes   However  if you want to code the names directly into your query  here is a cleaner way to do it   with names  fname lname  as       values           John   Smith              Mary   Jones     select city from user     inner join names on         fname firstName and         lname lastName    The advantage of this is that it separates your data out of the query somewhat    This is DB2 syntax  it may need a bit of tweaking on your system

User · Answer

In general you can easily write the Where-Condition like this   select   from tab1 where  col1  col2  in  select col1  col2 from tab2    Note Oracle ignores rows where one or more of the selected columns is NULL  In these cases you probably want to make use of the NVL-Funktion to map NULL to a special value  that should not be in the values    select   from tab1 where  col1  NVL col2   ---   in  select col1  NVL col2   ---   from tab2    oracle sql

User · Answer

Ensure you have an index on your firstname and lastname columns and go with 1   This really won t have much of a performance impact at all   EDIT  After  Dems comment regarding spamming the plan cache  a better solution might be to create a computed column on the existing table  or a separate view  which contained a concatenated Firstname   Lastname value  thus allowing you to execute a query such as   SELECT City  FROM User  WHERE Fullname in   fullnames    where  fullnames looks a bit like   JonDoe    JaneDoe   etc

User · Answer

In Oracle you can do this   SELECT   FROM table1 WHERE  col a col b  IN  SELECT col x col y FROM table2

User · Answer

You could do like this   SELECT city FROM user WHERE  firstName  lastName  IN    a    b      c    d       The sqlfiddle

[sql] SQL multiple columns in IN clause

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