Case study about how to find out suitable index - http://samsaffron.com/archive/2011/05/02/A+day+in+the+life+of+a+slow+page+at+Stack+Overflow#

A simple example of how to use EXPLAIN to find out the bottleneck of the query and add suitable index to suitable column - http://hackmysql.com/case4

Bitmap Index vs. B-tree Index: Which and When? - http://www.oracle.com/technology/pub/articles/sharma_indexes.html http://publib.boulder.ibm.com/infocenter/iseries/v5r3/index.jsp?topic=/rzajq/perf21c.htm

script to check if index is missing at foreign key
<pre>
select table_name, constraint_name,
       cname1 || nvl2(cname2,','||cname2,null) ||
       nvl2(cname3,','||cname3,null) || nvl2(cname4,','||cname4,null) ||
       nvl2(cname5,','||cname5,null) || nvl2(cname6,','||cname6,null) ||
       nvl2(cname7,','||cname7,null) || nvl2(cname8,','||cname8,null)
              columns
    from ( select b.table_name,
                  b.constraint_name,
                  max(decode( position, 1, column_name, null )) cname1,
                  max(decode( position, 2, column_name, null )) cname2,
                  max(decode( position, 3, column_name, null )) cname3,
                  max(decode( position, 4, column_name, null )) cname4,
                  max(decode( position, 5, column_name, null )) cname5,
                  max(decode( position, 6, column_name, null )) cname6,
                  max(decode( position, 7, column_name, null )) cname7,
                  max(decode( position, 8, column_name, null )) cname8,
                  count(*) col_cnt
             from (select substr(table_name,1,30) table_name,
                          substr(constraint_name,1,30) constraint_name,
                          substr(column_name,1,30) column_name,
                          position
                     from sys.user_cons_columns ) a,
                  sys.user_constraints b
            where a.constraint_name = b.constraint_name
              and b.constraint_type = 'R'
            group by b.table_name, b.constraint_name
         ) cons
   where col_cnt > ALL
           ( select count(*)
               from sys.user_ind_columns i
              where i.table_name = cons.table_name
                and i.column_name in (cname1, cname2, cname3, cname4,
                                      cname5, cname6, cname7, cname8 )
                and i.column_position <= cons.col_cnt
              group by i.index_name
           ) 
</pre>
http://chriswongdevblog.blogspot.com.au/2013/01/dont-forget-to-index-your-oracle.html

Explain how postgres indexes work, look like combine index is not that useful - http://dublintech.blogspot.com.au/2015/07/postgres-indexes.html

SQL Server JDBC – Set sendStringParametersAsUnicode to false - https://vladmihalcea.com/sql-server-jdbc-sendstringparametersasunicode/