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How to generate trace file – SQL Trace and TKPROF in Oracle
It is a frequently asked question in almost all the Oracle forums. There have had been numerous questions/posts regarding “But how to generate the trace file?” Well, it might seem a heck of a task,...
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SQL*Plus error logging – New feature release 11.1
One of the most important things that a developer does apart from just code development is, debugging. Isn’t it? Yes, debugging the code to fix the errors that are raised. But, in order to actually...
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Oracle – Case Insensitive Sorts & Compares
Oracle enhanced it’s case-insensitive sorts and compares feature with 10g Release 2. Version 11g has the following types of sorts: • Binary sort • Monolingual linguistic sort • Multilingual linguistic...
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Understanding Oracle Deadlock
Being a database application developer, a lot of times we come across deadlock errors. We know that a deadlock detected message is actually a clue to understand that it is a application design level...
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Oracle – Insert Comma separated string values into Table
This is a small demonstartion of how to insert the values of a comma separated string to a table as different rows. This is not something new, Tom Kyte has already demonstrated it lot of times in...
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ORA-06503: PL/SQL: Function returned without value
An important thing regarding function, you would agree with me that, at least once a PL/SQL developer must have heard that “A function MUST ALWAYS RETURN a VALUE of proper datatype”. Having been said...
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WHEN OTHERS THEN NULL – A bug
A when others is almost always a BUG unless it is immediately followed by a RAISE. — Quote from Thomas Kyte’s excellent thread on similar topic Remember, for errors, RAISE –>...
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SQL*Plus error logging – workaround for ROLLBACK issue
In my previous post SQL*Plus error logging – New feature release 11.1, as a NOTE I stated an issue that whenever ROLLBACK is issued in the session, the feature fails to log the errors. Thanks to Jacek...
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Oracle EXPLAIN PLAN – How to create, display and read
This post is to demonstrate the ways to create and display explain plan. But before we proceed with the steps of creating and displaying explain, the schema must have the PLAN_TABLE. A lot of times...
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Order of item list in declaration part of PL/SQL anonymous block – PLS-00103
In an anonymous PL/SQL block, if you do not follow the order of the item list in the declaration part, you might just end up with PLS-00103 error. Per Oracle documentation on Anonymous Block following...
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PL/SQL Developer Settings
Being an Oracle database application developer, we come across a lot of client tools like SQL*Plus, SQL Developer, TOAD, PL/SQL Developer etc. In this post I will be explaining the most common settings...
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Lock user SYS and Connect without SYSDBA
Many times this question comes up “Whether we could login as SYS but not as SYDBA”. Related questions are “Whether you could lock SYS account”. The answer to both the questions is YES. Let’s see how :...
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A myth about Row Exclusive Table Lock on SELECT FOR UPDATE with no rows
Recently I came across a question in Stackoverflow about row exclusive lock after executing SELECT..FOR UPDATE with no rows selected. The fact was that the query returned no rows, but Oracle applies a...
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V$RESERVED_WORDS & X$KWDDEF – Interesting facts!
It’s a lazy Friday and I saw an interesting question in Stackoverflow about “Why are there two “null” keywords in Oracle’s v$reserved_words view?” And I spent next 2 hours digging into knowing the...
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Find specific/similar words in a string using REGULAR EXPRESSION in Oracle
This is supposed to be one of the most common question among all the Oracle discussion forums, and especially folks looking for REGULAR EXPRESSION over web, would have definitely come across such a...
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Why are junk values/special characters/question marks displayed on my client?
There have been numerous questions on almost all the Oracle discussion forums about “Why are junk values displayed on my client” or ” Why do I see question marks or special characters in the table”....
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Find all columns having at least a NULL value from all tables in the schema
Spending a good amount of time answering the questions on multiple Oracle forums, like OraFAQ, Stack Overflow, OTN, dBforums etc. I could now figure out the most common questions by amateurs in Oracle...
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Oracle 12c Post Installation Mandatory Steps
Since 12c was made available for Windows 64bit OS Desktop class, people started using it immediately. And, some/few/most/all must have encountered issues while installation and especially post...
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SYS_OP_C2C Oracle internal function, implicit conversion and performance impact
SYS_OP_C2C is an internal function which does an implicit conversion of varchar2 to national character set using TO_NCHAR function. SQL> CREATE TABLE t AS SELECT 'a'||LEVEL col FROM dual CONNECT BY...
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Split single comma delimited string into rows in Oracle
NOTE : This post is about splitting a single comma delimited string. If you have to apply it on a table with multiple rows having comma delimited strings, then look at Split comma delimited strings in...
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DBMS_UTILITY.COMMA_TO_TABLE
The DBMS_UTILITY package provides various utility subprograms. One such useful utility is COMMA_TO_TABLE procedure, which converts a comma-delimited list of names into a PL/SQL table of names. Let’s...
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Quoting string literal technique to avoid errors due to single-quotation...
I have seen many questions on the Oracle forums on how to avoid the error due to single-quotation marks in the string literal. One such question was...
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Flashback DML changes on a table after COMMIT
I see frequent questions regarding “How to Rollback database changes after commit” or “How to flashback my table to previous state”. One such questions was asked here...
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Varying IN list of values in WHERE clause
One of the frequent question on Oracle forums is about the Varying IN list in WHERE clause. One such question was asked here...
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SQL to Search for a VALUE in all COLUMNS of all TABLES in an entire SCHEMA
One of the tricky questions asked in almost all the Oracle forums “How to search for a VALUE in all COLUMNS of all TABLES in an entire SCHEMA”. One such question is asked in Stack Overflow...
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Auto-increment primary key in Pre 12c releases (Identity functionality)
Oracle 12c has introduced the IDENTITY COLUMN functionality which provides an automatic functionality of a trigger-sequence approach for populating the primary key of a table. However, for Pre 12c...
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IDENTITY column autoincrement functionality in Oracle 12c
Oracle 12c has introduced the IDENTITY column which is the automatic method over the old trigger-sequence based approach to auto-populate the primary key of a table. In my previous post, Auto-increment...
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Why *_PROCEDURES view doesn’t show the PROCEDURE_NAME
Recently I saw a question in Stack Overflow “Unable to find procedure in DBA_PROCEDURES view“. Similar questions are: Why can’t I see my procedure in user_procedures view? Why is the procedure_name...
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Split comma delimited strings in a table in Oracle
NOTE : This post is about splitting multiple comma delimited column values in a table. If you have to apply it on a single value then look at Split single comma delimited string into rows in Oracle In...
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Performance difference between Explicit and Implicit Cursors in Oracle PL/SQL
There are many articles over the web about the difference between an explicit and implicit cursor. Theoretically, an implicit cursor is nicer and way faster. For an implicit cursor, Oracle takes care...
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Why DELETE takes longer than INSERT
There was a question on Stack Overflow why does delete take longer than insert. The question is too broad to be addressed as there could be many reasons and statistics behind the two operations....
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Returning the sequence number of Identity column after Insert
One of the frequently asked questions about sequences is “How to return the last sequence inserted?” Now, with the introduction of Identity column, I saw a similar question in Stack Overflow, Returning...
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Reverse the order of comma separated string using Oracle SQL
There was a question on Stack Overflow about “Oracle:how to reverse the string ‘ab,cd,ef’ to ‘ef->cd->ab’” Now, the question might look straight forward to simply reverse the string. However, it...
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Generate Date, Month Name, Week Number, Day number between two dates in...
This is a frequently asked question in most of the forums. Recently saw such question in Stack Overflow Generate Month Name, Day name, Week number and Day number between two dates. Typical questions...
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Why not use WM_CONCAT function in Oracle?
String aggregation related questions are frequently asked questions and every now and then someone provides a solution using WM_CONCAT function. And it really annoys me to repeat the same thing every...
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UTL_MATCH string comparision technique in Oracle
The UTL_MATCH package facilitates matching two records. It comes very handy for data entry validation and string matching. Setup DROP TABLE t_utl_match; CREATE TABLE t_utl_match ( id NUMBER, col1...
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Find range of consecutive values in a sequence of numbers or dates
One of the frequently asked questions is about Gaps and Islands problems which involve finding a range of missing values (gaps) or a range of consecutive values (islands) in a sequence of numbers or...
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Find range of missing values in a sequence of numbers or dates
One of the frequently asked questions is about Gaps and Islands problems which involve finding a range of missing values (gaps) or a range of consecutive values (islands) in a sequence of numbers or...
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Outer-joins Oracle vs ANSI syntax
this is one of the frequently asked questions about the use of “+” operator in Oracle join syntax. For beginners it is usually a confusion to interpret the different syntax. One of the good reasons to...
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Oracle String Aggregation Techniques
This is a frequently asked question “How to display multiple rows in a single row as a delimited string”. It is basically string aggregation. I will demonstrate the various techniques of string...
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root.sh : Enter the full pathname of the local bin directory
While installing Oracle using Oracle Universal Installer (OUI), there are few scripts which needs to be run as “root” user in the OS. One such script is the “root.sh” which resides in $ORACLE_HOME....
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ORA-12547: TNS :lost contact when try to connect to Oracle
ERROR: ORA-12547: TNS :lost contact when try to connect to Oracle There could be many reasons for the above error, but one of the common issue is due to incorrect permissions to the oracle binaries in...
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sqlplus / as sysdba : ORA-01031: insufficient privileges
ERROR: ORA-01031: insufficient privileges If you get the above error with / as sysdba i.e. when you are trying to connect to LOCAL instance as specified in the environment variables ORACLE_HOME and...
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ORA-12578: TNS:wallet open failed
If you get the following error message: ORA-12578: TNS:wallet open failed then edit your sqlnet.ora file and modify SQLNET.WALLET_OVERRIDE parameter value from TRUE to FALSE. Change this:...
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