The SQL LENGTH function returns the number of characters in a string. The LENGTH function is available in many Database Management Systems (DBMS).
The LENGTH Function Syntax
LENGTH Function Notes
If the input string is empty, the LENGTH returns 0.
If the input string is NULL, the LENGTH returns NULL.
Length Function Across Databases
When working as a technical consultant, one has to work with customer’s databases and as you move from one database to another you will find that the function commands may vary–assuming the database has an equivalent function.
Working with VQL and SQL Server got me thing about the LENGTH() function, so, here is a quick references list, which does include the SQL Server.
PostgreSQL is an open-source database, which was released in
1996. So, PostgreSQL has been around a long time. So, among the many companies and industries
which know they are using PostgreSQL, many others are using PostgreSQL and
don’t know it because it is embedded as the foundation in some other
application’s software architecture.
I hadn’t paid much attaint to PostgreSQL even though it as
been on the list leading databases used by business for years. Mostly I have been focused on the databases
my customer were using (Oracle, DB2, Microsoft SQL Server, and MySQL/MariaDB). However, during a recent meeting I was
surprised to learn that io had been using and administering PostrgresSQL embedded
as part of another software vendors application, which made me take the time to
pay attention to PostgreSQL. Especially, who is using PostgreSQL and what opportunities
that may provide for evolving my career?
Industries Using PostgreSQL
According to enlyft,
the major using the PostgreSQL are Computer Software and Information Technology
And services companies.
PostgreSQL Consumers Information
Here is the link to
enlyft page, which provides additional information companies and industries
Well, this is one of those circumstances, where your ability
to answer this question will depend upon your user’s assigned security roles
and what you actually want.
To get a complete list, you will need to use the DBA_
administrator tables to which most of us will not have access. In the very simple examples below, you may
want to add a WHERE clause to eliminate the system schemas from the list, like
‘SYS’ and ‘SYSTEM,’ if you have access to them.
Administrator (DBA) Schema List
SELECT distinct OWNER as SCHEMA_NAME
ORDER BY OWNER;
(DBA) Schema List Results Screenshot
Fortunately for the rest of us, there are All user tables,
from which we can get a listing of the schemas to which we have access.
All Users Schema List
SELECT distinct OWNER as SCHEMA_NAME
ORDER BY OWNER;
Example All Users
Schema List Results Screenshot
Oracle help Center
> Database> Oracle > Oracle Database > Release 19
It is funny how you cannot work with some for a while
because of newer tools, and then rediscover them, so to speak. The other day I was looking at my overflow
bookshelf in the garage and saw an old book on Oracle SQL*Plus and was thinking,
“do I still want or need that book?”.
In recent years I have been using a variety of other tools
when working with oracle. So, I really hadn’t thought about the once ubiquitous
Oracle SQL*Plus command-line interface for Oracle databases, which around for
thirty-five years or more. However, I
recently needed to do an Oracle 18C database install to enable some training
and was pleasantly surprised Oracle SQL*Plus as a menu item.
Oracle provides a few ways to determine which database you are working in. Admittedly, I usually know which database I’m working in, but recently I did an Oracle Database Express Edition (XE) install which did not goes has expected and I had reason to confirm which database I was actually in when the SQL*Plus session opened. So, this lead me to consider how one would prove exactly which database they were connected to. As it happens, Oracle has a few ways to quickly display which database you are connected to and here are two easy ways to find out your Oracle database name in SQL*Plus:
the GLOBAL_NAME table
The First method is to run a quick-select against the GLOBAL_NAME
table, which. is publicly available to logged-in users of the database
Example GLOBAL_NAME Select Statement
select * from global_name;
the V$DATABASE Variable
The second method is to run a quick-select a V$database.
However, not everyone will have access to the V$database variable.
While investigating a recent Infosphere Information Server (IIS), Datastage, Essbase Connect error I found the explanations of the probable causes of the error not to be terribly meaningful. So, now that I have run our error to ground, I thought it might be nice to jot down a quick note of the potential cause of the ‘Client Commands are Currently Not Being Accepted’ error, which I gleaned from the process.
Error Message Id
An error occurred while processing the request on the server. The error information is 1051544 (message on contacting or from application:[<<DateTimeStamp>>]Local////3544/Error(1013204) Client Commands are Currently Not Being Accepted.
Possible Causes of The Error
This Error is a problem with access to the Essbase object or accessing the security within the Essbase Object. This can be a result of multiple issues, such as:
Object doesn’t exist – The Essbase object didn’t exist in the location specified,
Communications – the location is unavailable or cannot be reached,
Path Security – Security gets in the way to access the Essbase object location
Essbase Security – Security within the Essbase object does not support the user or filter being submitted. Also, the Essbase object security may be corrupted or incomplete.
Essbase Object Structure – the Essbase object was not properly structured to support the filter or the Essbase filter is malformed for the current structure.
IBM Knowledge Center, InfoSphere Information Server 11.7.0, Connecting to data sources, Enterprise applications, IBM InfoSphere Information Server Pack for Hyperion Essbase
While working with a client’s 9.1 DataStage version, I ran into a situation where they wanted to parameterize SQL where clause lists in an Oracle Connector stage, which honestly was not very straight forward to figure out. First, if the APT_OSL_PARAM_ESC_SQUOTE is not set and single quotes are used in the parameter, the job creates unquoted invalid SQL when the parameter is populated. Second, I found much of the information confusing and/or incomplete in its explanation. After some research and some trial and error, here is how I resolved the issue. I’ll endeavor to be concise, but holistic in my explanation.
When this Variable applies
This where I know this process applies, there may be other circumstances to which is this applicable, but I’m listing the ones here with which I have recent experience.
Infosphere Information Server Datastage
Versions 91, 11.3, and 11.5
Versions 11g and 12c
Here is a brief explanation of the steps I used to implement the where clause as a parameter. Please note that in this example, I am using a job parameter to populate on a portion of the where clause, you can certainly pass the entire where clause as a parameter, if it is not too long.
Configure Project Variable in Administrator
Add APT_OSL_PARAM_ESC_SQUOTE to project in Administrator
Populate the APT_OSL_PARAM_ESC_SQUOTE Variable
Create job parameter
Following your project name convention or standard practice, if you customer and/or project do not have established naming conventions, create the job parameter in the job. See jp_ItemSource parameter in the image below.
Add job parameter to Custom SQL in Select Oracle Connector Stage
On the Job parameter has been created, add the job parameter to the SQL statement of the job.
IBM Knowledge Center > InfoSphere Information Server 11.5.0
Connecting to data sources > Databases > Oracle databases > Oracle connector
I’ve tried to explain the difference between OLTP systems and a Data Warehouse to my managers many times, as I’ve worked at a hospital as a Data Warehouse Manager/data analyst for many years. Why was the list that came from the operational applications different than the one that came from the Data Warehouse? Why couldn’t I just get a list of patients that were laying in the hospital right now from the Data Warehouse? So I explained, and explained again, and explained to another manager, and another. You get the picture. In this article I will explain this very same thing to you. So you know how to explain this to your manager. Or, if you are a manager, you might understand what your data analyst can and cannot give you.
OLTP stands for On Line Transactional Processing. With other words: getting your data directly from the operational systems to make reports. An operational system is a system that is used for the day to day processes. For example: When a patient checks in, his or her information gets entered into a Patient Information System. The doctor put scheduled tests, a diagnoses and a treatment plan in there as well. Doctors, nurses and other people working with patients use this system on a daily basis to enter and get detailed information on their patients. The way the data is stored within operational systems is so the data can be used efficiently by the people working directly on the product, or with the patient in this case.
A Data Warehouse is a big database that fills itself with data from operational systems. It is used solely for reporting and analytical purposes. No one uses this data for day to day operations. The beauty of a Data Warehouse is, among others, that you can combine the data from the different operational systems. You can actually combine the number of patients in a department with the number of nurses for example. You can see how far a doctor is behind schedule and find the cause of that by looking at the patients. Does he run late with elderly patients? Is there a particular diagnoses that takes more time? Or does he just oversleep a lot? You can use this information to look at the past, see trends, so you can plan for the future.
The difference between OLTP and Data Warehousing
This is how a Data Warehouse works:
The data gets entered into the operational systems. Then the ETL processes Extract this data from these systems, Transforms the data so it will fit neatly into the Data Warehouse, and then Loads it into the Data Warehouse. After that reports are formed with a reporting tool, from the data that lies in the Data Warehouse.
This is how OLTP works:
Reports are directly made from the data inside the database of the operational systems. Some operational systems come with their own reporting tool, but you can always use a standalone reporting tool to make reports form the operational databases.
Pro’s and Con’s
There is no strain on the operational systems during business hours
As you can schedule the ETL processes to run during the hours the least amount of people are using the operational system, you won’t disturb the operational processes. And when you need to run a large query, the operational systems won’t be affected, as you are working directly on the Data Warehouse database.
Data from different systems can be combined
It is possible to combine finance and productivity data for example. As the ETL process transforms the data so it can be combined.
Data is optimized for making queries and reports
You use different data in reports than you use on a day to day base. A Data Warehouse is built for this. For instance: most Data Warehouses have a separate date table where the weekday, day, month and year is saved. You can make a query to derive the weekday from a date, but that takes processing time. By using a separate table like this you’ll save time and decrease the strain on the database.
Data is saved longer than in the source systems
The source systems need to have their old records deleted when they are no longer used in the day to day operations. So they get deleted to gain performance.
You always look at the past
A Data Warehouse is updated once a night, or even just once a week. That means that you never have the latest data. Staying with the hospital example: you never knew how many patients are in the hospital are right now. Or what surgeon didn’t show up on time this morning.
You don’t have all the data
A Data Warehouse is built for discovering trends, showing the big picture. The little details, the ones not used in trends, get discarded during the ETL process.
Data isn’t the same as the data in the source systems
Because the data is older than those of the source systems it will always be a little different. But also because of the Transformation step in the ETL process, data will be a little different. It doesn’t mean one or the other is wrong. It’s just a different way of looking at the data. For example: the Data Warehouse at the hospital excluded all transactions that were marked as cancelled. If you try to get the same reports from both systems, and don’t exclude the cancelled transactions in the source system, you’ll get different results.
online transactional processing (OLTP)
You get real time data
If someone is entering a new record now, you’ll see it right away in your report. No delays.
You’ve got all the details
You have access to all the details that the employees have entered into the system. No grouping, no skipping records, just all the raw data that’s available.
You are putting strain on an application during business hours.
When you are making a large query, you can take processing space that would otherwise be available to the people that need to work with this system for their day to day operations. And if you make an error, by for instance forgetting to put a date filter on your query, you could even bring the system down so no one can use it anymore.
You can’t compare the data with data from other sources.
Even when the systems are similar. Like an HR system and a payroll system that use each other to work. Data is always going to be different because it is granulated on a different level, or not all data is relevant for both systems.
You don’t have access to old data
To keep the applications at peak performance, old data, that’s irrelevant to day to day operations is deleted.
Data is optimized to suit day to day operations
And not for report making. This means you’ll have to get creative with your queries to get the data you need.
So what method should you use?
That all depends on what you need at that moment. If you need detailed information about things that are happening now, you should use OLTP. If you are looking for trends, or insights on a higher level, you should use a Data Warehouse.
Since the Infosphere, information server, repository, has to be installed manually with the scripts provided in the IBM software, sometimes you run into difficulties. So, here’s a quick script, which I have found useful in the past to identify user permissions for the IAUSER on Oracle database’s to help rundown discrepancies in user permissions.
WHERE GRANTEE = ‘iauser’
If we cannot run against the ALL_TAB_PRIVS view, then we can try the ALL_TAB_PRIVS view:
WHERE GRANTEE = ‘iauser’
oracle help Center > Database Reference > ALL_TAB_PRIVS view
Here is a table quick reference of some common database and/or connection types, which use connection level isolation and the equivalent isolation levels. This quick reference may prove useful as a job aid reference, when working with and making decisions about isolation level usage.
Oracle doesn’t recognize the ’Limit’ command, however, there is any easy way to achieve the same result. Using the Oracle/function in the ‘where’ clause.
ROWNUM Pseudo Column Description
The Oracle/PLSQL ROWNUM pseudo column returns a number that represents the order that a row is selected by Oracle from a table or joined tables. The first row has a ROWNUM of 1, the second has a ROWNUM of 2, and so on.
Basic RUWNUM Syntax
WHERE ROWNUM <= number
Order by column_name(s);
Example SQL Limiting to One row
The one row limit has two accurate way to get the desired result:
· SQL Limiting to One row using equal to
where rownum = 1;
· SQL Limiting to One row using less than or equal to
This jdbc information is based on Oracle Database 11g Release 2 (18.104.22.168), on a RAC (Oracle Real Application Clusters), JDBC for InfoSphere Information Server11.5 on Red Hat Linux. so, here are a few pointers for building an IBM InfoSphere Information Server (IIS) isjdbc.config file.
Where to place JAR files
For Infosphere Information Server installs, as a standard practice, create a custom jdbc folder in the install path and copy the jar file into the folder (not install activity required). Usually, jdbc folder path looks something like this:
JAR Source URL
In this example, we used the jar files from the client install, but if you want to skip the client install you can download the drivers here: Oracle JDBC Drivers
Oracle DEFAULT PORT
JDBC URL FORMAT
JDBC URL EXAMPLE
Create And Place A jdbc configuration file
The Isjdbc.config file needs to be placed in the DSEngine directory:
Tuning SQL is one of those skills, which is part art and part science. However, there are a few fundamental approaches, which can help ensure optimal SQL select statement performance.
Structuring your SQL
By Structuring SQL Statements, much performance can be gained through good SQL statement organization and sound logic.
Where Clause Concepts:
Use criteria ordering and Set Theory thinking. SQL can be coupled with set-theory to aid conception of the operations being conducted. Order your selection criteria to execute criteria which arrives at the smallest possible row set first. Doing so reduces the volume of rows to be processed by follow-on operations. This does require an understanding of the data relationships to be effective.
Join Rules (equijoins, etc.)
When constructing your joins, consider these rules:
Join on keys and indexed columns: The efficiency of your program improves when tables are joined based on indexed columns, rather than on non-indexed ones.
Use equijoins (=), whenever possible
Avoid using of sub-queries
Re-write EXISTS and NOT EXISTS subqueries as outer joins
Avoid OUTER Joins on fields containing nulls
Avoid RIGHT OUTER JOINS: Always select FROM your primary table (or derived table) and LEFT OUTER JOIN to auxiliary tables.
Use Joins Instead of Subqueries: A join can be more efficient than a correlated subquery or a subquery using IN. Use caution when specifying ORDER BY with a Join: When the results of a join must be sorted, limiting the ORDER BY to columns of a single table can cause the database to avoid a sort.
Provide Adequate Search Criteria: When possible, provide additional search criteria in the WHERE clause for every table in a join. These criteria are in addition to the join criteria, which are mandatory to avoid Cartesian products
Order of Operations SQL & “PEMDAS”
To improve your SQL, careful attention needs to be paid to the mathematical order of operations; especially, parentheses since they not only set the order of operation but also the boundaries of each subset operation.
PEMAS is “Parentheses, Exponents, Multiplication and Division, and Addition and Subtraction”.
Use parentheses () to group and specify the order of execution. SQL observes the normal rules of arithmetic operator precedence.
If the parentheses are nested, the expression in the innermost pair is evaluated first. If there are several un-nested parentheses, then parentheses are evaluated left to right.
* / %
Multiplication Division Modulus
If there are several, evaluation is left to right.
If there are several, evaluation is left to right.
Index Leveraging (criteria ordering, hints, append, etc.)
Avoid Full Table Scans: within the scope of a SQL statement, there are many conditions that will cause the SQL optimizer to invoke a full-table scan.
with NULL Conditions (Is NUll, Is Not NUll)
Against Unindexed Columns
with Like Conditions
with Not Equals Condition (<>, !=, not in)
with use built-in Function (to_char, substr, decode, UPPER)
Use UNION ALL instead of UNION if business rules allow
UNION: Specifies that multiple result sets are to be combined and returned as a single result set. Query optimizer performs extra work to return to avoid duplicate rows.
UNION ALL: Incorporates all rows into the results. This includes duplicates. Query optimizer just needs to concatenate the result sets with no extra work
Use stored procedures instead of ad hoc queries when possible. Stored procedures are precompiled and cached
Avoid cursor use when possible
Select only the rows needed
Use NOLOCK hint in the select statement to avoid blocking
Commit transactions in smaller batches
Whenever possible use tables instead of views
Make sure comparison columns whether using JOIN or WHERE clause are exactly the same data type. For example, if we are comparing Varchar column to nchar columns the query optimizer has to do a CONVERT before comparing the values
Note: You do not necessarily need to remove all full table scans from your query’s execution plan. Tables with few rows, few columns, or thin columns may fit into few database blocks. In this case, a full table scan will always be the most efficient access
Sometimes, when converting fields from text to numeric fields in SQL, there is a need to remove one or more non-numeric values. These approaches have been useful for handling multiple non-numeric values.
Removing non-numeric values – Approach 1:
I have found this approach useful when working with character (Char, Varchar, NVARCHAR) fields being converted to non-integers outputs (e.g. Decimal).
CAST(( CASE WHEN TRIM(<<SourceFieldName>>) > ‘9999999999’ or length(REGEXP_SUBSTR(<<SourceFieldName>>, ‘[A-z]’, 1, 1))>0 or trim(<<SourceFieldName>>) in (‘-‘,’+’,’?’,’/’,’*’) THEN NULL ELSE trim(<<SourceFieldName>>) END) AS DECIMAL(10,2)) AS <<TargetFieldName>>,
Removing non numeric values – Approach 2:
If you need to know if a content of a field is numeric, I have most this approach useful when working with character (Char, Varchar, NVARCHAR) fields being converted to integers:
CAST(( CASE WHEN LENGTH(TRANSLATE(<<SourceFieldName>>,’0123456789′,”))=0 THEN (<<SourceFieldName>> ELSE NULL END) as INTEGER) as <<TargetFieldName>>,
In PeopleSoft (PS) query, it is possible to add the user name of the person who ran the query as a column. To do so create an expression, substring the %Operator global variable, and use the expression as a field.
I’ve had this SQL snippet laying around for a while, so, before I lose it, I thought I would post it for future reference. Below is SQL to lookup a XLAT values, in case you don’t want to or cannot go through PeopleSoft Application Designer.