All columns of table should be indexed or not mysql database?

Question

I want to make one table with 4 columns. One is the primary key and the other three columns are references to columns of other tables. I want to use it to join these four tables to make a search filter. These joins are taking time.

I was thinking I should index these columns because I read that adding indexes on column used in join conditions [makes them run faster]. My question is will there be a problem if all columns of the table are indexed? Or is there any other way to decrease time complexity of the search filter. Thanks in advance.

More Hint: Table1(main search)-1000 entries primary_key fk1 fk2 fk3

Table2-800 entries pk1 ..(8-9 columns)

Table3-700 entries pk2 ..(10-12 columns)

Table2-850 entries pk3 ..(7-8 columns)

Answer 1

Creating an index requires additional disk space, and that too many indexes can cause issues arising from the file systems size limits, careful thought must be used to select the correct fields to index.

Since indexes are only used to speed up the searching for a matching field within the records, it stands to reason that indexing fields used only for output would be simply a waste of disk space and processing time when doing an insert or delete operation, and thus should be avoided. Also given the nature of a binary search, the cardinality or uniqueness of the data is important. Indexing on a field with a cardinality of 2 would split the data in half, whereas a cardinality of 1,000 would return approximately 1,000 records. With such a low cardinality the effectiveness is reduced to a linear sort, and the query optimizer will avoid using the index if the cardinality is greater than 30% of the record number, effectively making the index a waste of space.

So better to add indexing on group of columns.