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Practical advice for database developers
Updated: 14 hours 25 min ago

ORA-01017 invalid username/password; logon denied Solution

Wed, 2017-02-01 05:00
Have you gotten an ORA-01017 error in your Oracle database? Learn what caused it and how you can resolve it in this article. ORA-01017 Cause So you’re trying to connect to a database, or run a query across a database link, and you get this message: ORA-01017: invalid username/password; logon denied There are a few […]
Categories: Development

Oracle SQL List Tables in Database or Schema

Mon, 2017-01-30 05:00
Do you need to list all tables in Oracle? There isn’t an SQL list tables command, but you can learn how to do show all tables in this article. Oracle SQL List Tables If you’ve forgotten the name of a specific table, or forgotten how to spell a table (was it plural or singular? One word […]
Categories: Development

ORA-00942 table or view does not exist Solution

Fri, 2017-01-27 05:00
Have you gotten an ORA-00942 error? I’ll explain the cause and the solution of the error in this article. ORA-00942 Cause The error message appears when you try to run an SQL statement: ORA-00942: table or view does not exist This happens for one of many reasons: The statement references a table or view that […]
Categories: Development

Weekly Link Roundup – Jan 27, 2017

Thu, 2017-01-26 17:57
This week I’ve read a few interesting articles on Oracle and I thought I’d share them here. RI (Referential Integrity) Constraints: 3 Reasons to Include Them in Your Data Warehouse Kent Graziano from The Data Warrior (and Snowflake) wrote an interesting article on using referential integrity constraints inside a data warehouse. I haven’t really considered […]
Categories: Development

ORA-00904 invalid identifier Solution

Wed, 2017-01-25 05:00
Did you get an “ORA-00904: invalid identifier” error? Find out what caused the ORA-00904 error and how to resolve it in this article. ORA-00904 Cause So, you ran an SQL statement and you got this error: ORA-00904: invalid identifier What causes this error? It’s caused by referring to a column that does not exist, or […]
Categories: Development

Oracle Triggers – The Complete Guide

Mon, 2017-01-23 05:00
Oracle triggers are a handy but often misused function of the Oracle database. Learn all about them in this article. Table of Contents This is a long article, so here’s a table of contents you can use to navigate around the page: What are Oracle Triggers? Types of Triggers in Oracle Reasons to Use Oracle […]
Categories: Development

Oracle VAR_POP Function with Examples

Fri, 2017-01-20 05:00
This article will explain the Oracle VAR_POP function and show you some examples. Purpose of the Oracle VAR_POP Function The VAR_POP function finds the population variance of a set of numbers, excluding NULLs. What does this mean? The population variance is a calculation that determines the difference or variation in a complete set of numbers. […]
Categories: Development

Weekly Link Roundup – Jan 20, 2017

Thu, 2017-01-19 18:02
Here’s my weekly link roundup for Jan 20, 2017. What Is This Link Roundup? A “link roundup” is a type of post on a website where the author collates a list of articles they have read recently, and adds them all into a single post. The aim is to make the readers of the site […]
Categories: Development

Oracle VAR_SAMP Function with Examples

Thu, 2017-01-19 05:00
In this article, I’ll explain the Oracle VAR_SAMP function and show you some examples. Purpose of the Oracle VAR_SAMP Function The VAR_POP function will return the sample variance of a set of numbers, after excluding NULLs. What does this mean? The sample variation calculates the variation of a sample of numbers from the overall set. […]
Categories: Development

What’s The Difference Between Oracle ROWNUM vs Oracle ROW_NUMBER?

Mon, 2017-01-16 05:00
Have you seen ROWNUM and ROW_NUMBER in Oracle and wondered what the difference is? Learn what they are and the differences between Oracle ROWNUM vs Oracle ROW_NUMBER in this article. What Is Oracle ROWNUM? You might think that ROWNUM is a function in Oracle. However, it’s not a function. It’s a “pseudocolumn”. It acts like […]
Categories: Development

Announcing “Database Star Academy”

Fri, 2017-01-13 20:03
All of the online courses I have created used to be on a separate site of mine called Software Developer Academy. These have now all been moved to a new section under my main site, called Database Star Academy. Read on to find out more. What Is Database Star Academy? It’s the name of a membership section on […]
Categories: Development

Oracle TO_MULTI_BYTE Function with Examples

Fri, 2017-01-13 05:00
In this article, I’ll be covering the Oracle TO_MULTI_BYTE function, and look at some examples. Purpose of the Oracle TO_MULTI_BYTE Function The TO_MULTI_BYTE function is used to convert a character string from single-byte characters to multi-byte characters. Your database must contain both single-byte and multi-byte characters for this function to be useful. If there are […]
Categories: Development

Oracle COVAR_POP Function with Examples

Thu, 2017-01-12 05:00
In this article, I’ll explain what the COVAR_POP function does and show you some examples. Purpose of the Oracle COVAR_POP Function The Oracle COVAR_POP function calculates the population covariance of a set of number pairs. What is a “population covariance”? Good question. Here’s an article that explains what the definition is. Just like the COVAR_SAMP […]
Categories: Development

What are the Differences Between a Primary Key vs Foreign Key?

Mon, 2017-01-09 05:00
I explain what a primary key and foreign key is, as well as the differences between primary key vs foreign key in this article. What Is a Primary Key? What is the primary key definition?  A primary key is one or more columns in a table that are used to uniquely identify the row. When […]
Categories: Development

Oracle COVAR_SAMP Function with Examples

Fri, 2017-01-06 05:00
In this article, I’ll explain what the Oracle COVAR_SAMP function does and show you some examples. Purpose of the Oracle COVAR_SAMP Function This function returns the covariance of a set of number pairs. What does that mean? Here’s an explanation of what a covariance is. This function, like the CORR and COVAR_POP function, can be run […]
Categories: Development

Oracle VSIZE Function with Examples

Thu, 2017-01-05 05:00
In this article, I’ll explain what the Oracle VSIZE function does and show you some examples. Purpose of the Oracle VSIZE Function The VSIZE function returns the number of bytes of an expression using the internal representation. That sounds a lot like the LENGTH function, doesn’t it? I’ll explain the differences shortly after we cover […]
Categories: Development

Singular vs Plural and Other Database Table Naming Conventions

Mon, 2017-01-02 05:00
Are you wondering if you should name your Oracle database tables in the singular form or plural form? Learn what the preferred convention is and some reasoning behind it, as well as other database table naming conventions, in this article. Why Do We Need SQL Table Naming Conventions? You might be wondering why we need conventions or […]
Categories: Development

Oracle INSTRB, INSTRC, INSTR2, and INSTR4 Function with Examples

Fri, 2016-12-30 05:00
In this article, I’ll explain what all of the variations of the INSTR function (INSTRB, INSTRC, INSTR2 and INSTR4) do, and show you some examples Purpose of the Oracle INSTR2, INSTR4, INSTRB, and INSTRC Functions These INSTR functions are variations of the basic INSTR function, which searches inside a string for a substring, and returns […]
Categories: Development

Oracle LENGTH2, LENGTH4, LENGTHB, and LENGTHC Function with Examples

Thu, 2016-12-29 05:00
In this article, we’ll look at the variations of the Oracle LENGTH function – LENGTH2, LENGTH4, LENGTHB, and LENGTHC. Purpose of the Oracle LENGTH2, LENGTH4, LENGTHB, and LENGTHC Function The purpose of these LENGTH function variants is the same as the basic LENGTH function – to find the length of a specified string. However, the […]
Categories: Development

A Guide to the Oracle TRUNCATE TABLE Statement

Mon, 2016-12-26 05:00
The Oracle TRUNCATE TABLE statement is a useful statement for removing data in Oracle SQL. I’ll explain what the statement does and show you some examples in this article. What Does the Oracle TRUNCATE TABLE Statement Do? The Oracle TRUNCATE statement, or TRUNCATE TABLE statement, removes all data from a table. It’s similar to the […]
Categories: Development

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