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POHow can SELECT COUNT(*) different from count of all records in the table?
 

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  1. POHow can SELECT COUNT(*) different from count of all records in the table?
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    <p>So I have a table: </p> <pre><code>CREATE TABLE TABLE_NAME ( COLUMN_1 char(12) NOT NULL, COLUMN_2 char(2) NOT NULL, COLUMN_3 char(1) NOT NULL, COLUMN_4 int NOT NULL, COLUMN_5 char(2) NOT NULL, COLUMN_6 money NOT NULL, COLUMN_7 smallint NOT NULL, COLUMN_8 varchar(10) NOT NULL, COLUMN_9 smallint NOT NULL, COLUMN_10 datetime NOT NULL Primary Key (COLUMN_1, COLUMN_2, COLUMN_3) ) </code></pre> <p><code>SELECT COUNT(*)</code> returns a different value than <code>SELECT DISTINCT COUNT(*)</code>. How can this be possible?</p> <p>I also tried </p> <pre><code>SELECT COUNT(*) FROM ( SELECT COLUMN_1, COLUMN_2, COLUMN_3, COLUMN_4, COLUMN_5, COLUMN_6, COLUMN_7, COLUMN_8, COLUMN_9, COLUMN_10 FROM TABLE_NAME ) TMP </code></pre> <p>which returned the same count as the distinct query.</p> <p>I'm a little tired, so I hope I'm not missing something obvious, but I can't see how with a primary key and all fields being NOT NULL, there can be a different total count than the count of unique records. </p> <p>BTW, this is on Sybase ASE 15.</p> <p>The discrepancy is a hundred or so records out of a half million. I'm also seeing this problem in several other tables, but chose just one for the example.</p> <p>EDIT:</p> <p>I should mention for the sake of completeness that I discovered this problem when writing a simple job to completely copy this table to a remote database. My application was recording a certain number of read/write operations, but failed QA because the number of records in the source database differed from the number of records in the target database. Both values were obtained via COUNT(*); the count returned from the target (Oracle 10g) was the same as the number of read/write operations recorded by my app. As all fields on the source table are defined NOT NULL and a primary key is defined, I was at a loss to explain how my application was losing a tiny number of records.</p> <p>This is when I started using the alternate queries listed above, both of which agreed with my apps read/write count, as well as the COUNT(<em>) value returned from the target. In other words, the only value that did not match was the COUNT(</em>) on the source database.</p>
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    1. USDanny Beckett
    1. USIckster
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    1. COPlease check my answer.
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      1. POHow can SELECT COUNT(*) different from count of all records in the table?
      1. USPerformanceDBA
 

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