If you do not specify any columns, the database server removes all the distribution data for that table. You must have the DBA privilege or be the owner of the table to use this option. As the example shows, you drop the distribution data at the same time you update the statistical data that the low mode option generates.
Use the MEDIUM mode option to update the same statistics that you can perform with the low mode and also generate statistics about the distribution of data values for each specified column.
The database server places distribution information in the sysdistrib system catalog table. The constructed distribution is statistically significant. When you use the MEDIUM mode option, the data for the distributions is obtained by sampling a percentage of data rows. Because the data obtained by sampling is usually much smaller than the actual number of rows, this mode executes more quickly than the HIGH mode.
Because the data is obtained by sampling, the results might vary that is, different sample rows might produce different distribution results. If the results vary significantly, you can adjust the resolution percent or confidence level to obtain more consistent results.
This value can be roughly interpreted to mean that 95 percent of the time, the estimate is equivalent to that obtained from high distributions.
You must have the DBA privilege or be the owner of the table to create medium distributions. Use the HIGH mode option to update the same statistics that you can perform with the low mode and also generate statistics about the distribution of data values for each specified column.
The constructed distribution is exact. You must have the DBA privilege or be the owner of the table to create high distributions. If you use the HIGH mode option to update statistics, the database server can take considerable time to gather the information across the database, particularly a database with large tables. The HIGH keyword might scan each table several times for each column.
To minimize processing time, specify a table name and column names within that table. Use the Resolution clause to adjust the size of the distribution bin, designate whether or not to avoid calculating data on indexes, and with the Medium mode, to adjust the confidence level. This can be roughly interpreted as meaning that 95 percent of the time, the estimate produced by the MEDIUM keyword is equivalent to using high distributions.
The minimum confidence level is 0. The maximum confidence level is 0. Literal Number, p. For HIGH mode, the default value is 0. A distribution is a mapping of the data in a column into a set of column values. The contents of the column are divided into bins or ranges, each of which contains an equal portion of the column data.
For example, if one bin holds 2 percent of the data, 50 of these 2-percent bins hold all the data. A bin contains the particular range of data values that reflects the appropriate percentage of entries in the column. Distributions are constructed for other columns in the list, and the statement does not return an error. The amount of space that the DBUPSPACE environment variable specifies determines the number of times the database server scans the designated table to construct a distribution.
This option does not affect existing index information. Use this option to avoid the examination of index information that can consume considerable processing time. This option does not affect the recalculation of information on tables, such as the number of pages used, the number of rows, and fragment information.
The SPL routine must reside in the current database. In an ANSI-compliant database, specify the owner as the prefix to the routine name. The following table explains the keywords that you can use when you update routine statistics.
The sysprocplan system catalog table stores execution plans for SPL routines. Two actions update the sysprocplan system catalog table:. To collect statistics for a column that holds a user-defined data type, you must specify either medium or high mode.
When you use this option, the database server removes the row in the sysdistrib system catalog table that corresponds to the tableid and column. In addition, the database server removes any large objects that might have been created for storing the statistics information. You must have usage permissions on these routines. You can choose to convert the indexes one table at a time or for the entire database at one time.
Follow the conversion guidelines that are outlined in the Informix Migration Guide. Limiting the number of columns distributed speeds the update. Collectives on Stack Overflow. Learn more. Update statement with Join in Informix Ask Question. Asked 8 years ago. Active 4 years, 10 months ago. Viewed 2k times. Improve this question. Put the query in your update statement after Equlas to Symbol — Santhosh. Thanks for the reply It is taking forever and gives me the following error SocketTimeoutException: Read timed out If you think it would work, can you please write the whole statement for me..
Thanks — BKRaja. Hi ceinmart, thanks for the reply. But I am already using this query in a merge statement. I am not sure how efficient is using a merge inside another merge statement. Also, Its not just a simple assignment to do ON t1. It should be t1. Is there a way to get the value first, store it in a variable and then update? Add a comment. Active Oldest Votes. So you need to update the the ID of kaushal 2. So you need to update the the ID of solanki see the result Note how many rows you need to update here 2 First try your select query put into update query then you said it gaves error..
Improve this answer. My issue is that the two querirs I have specified works fine individually. I am just confused how to make two declarations for each of the two tables in both queries
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