Technical Blog Post
Abstract
How to check if any columns suffer from frequency value stats issue?
Body
Following query can be used to determine if any columns suffer from frequency value stats issue.
WITH FREQ (TABSCHEMA, TABNAME, COLNAME, FREQSUM, FREQCOUNT) AS (SELECT TABSCHEMA, TABNAME, COLNAME, SUM(VALCOUNT) FREQSUM, COUNT(VALCOUNT) FREQCOUNT FROM SYSSTAT.COLDIST WHERE TYPE = 'F' AND COLVALUE IS NOT NULL AND VALCOUNT > 0 GROUP BY TABSCHEMA, TABNAME, COLNAME) SELECT C.TABSCHEMA, C.TABNAME, C.COLNAME FROM FREQ, sysstat.columns AS C, sysstat.tables T WHERE FREQ.TABSCHEMA = C.TABSCHEMA AND FREQ.TABNAME = C.TABNAME AND FREQ.COLNAME = C.COLNAME AND C.TABSCHEMA = T.TABSCHEMA AND C.TABNAME = T.TABNAME AND T.CARD > 0 AND C.COLCARD > 0 AND (T.CARD - FREQ.FREQSUM) < (C.COLCARD - FREQ.FREQCOUNT)
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UID
ibm13286689