Substrings in SQL
Informix®
Informix SQL statements can use subscripts on columns defined with the character data type:
SELECT ... FROM tab1 WHERE col1[2,3] = 'RO'
SELECT ... FROM tab1 WHERE col1[10] = 'R' -- Same as col1[10,10]
UPDATE tab1 SET col1[2,3] = 'RO' WHERE ...
SELECT ... FROM tab1 ORDER BY col1[1,3]Important: With other database servers as Informix, when the subscript notation is used to modify column values in UPDATE statement, or
as ORDER BY element, you will get and SQL error:
UPDATE tab1 SET col1[2,3] = 'RO' WHERE ...
SELECT ... FROM tab1 ORDER BY col1[1,3]Netezza®
Netezza provides the SUBSTRING( ...
from ... to ... ) function, to extract a substring from a string expression:
SELECT .... FROM tab1 WHERE SUBSTRING(col1 from 2 for 2) = 'RO'
SELECT SUBSTRING('Some text' from 6 for 3) ... -- Gives 'tex'Solution
Replace all Informix col[x,y]
right-value expressions by SUBSTRING( col from x for (y-x+1) ).
Rewrite UPDATE and ORDER BY clauses using
col[x,y] expressions.
The translation of
col[x,y] expressions can be controlled with the following FGLPROFILE
entry:dbi.database.dsname.ifxemul.colsubs = { true | false }