Postgresql coalesce empty string String Functions and Operators # 9. In particular, sum of no rows returns null, not zero as one might expect, and array_agg returns null rather than an empty array when there are no input rows. The Problem: '' ≠ NULL in PostgreSQL. Jul 15, 2025 · Now, NULLIF converts empty strings to NULL, and COALESCE provides the body content for posts with no excerpt. It returns the first of its arguments that is not null. Aug 4, 2025 · Learn how PostgreSQL's COALESCE function efficiently handles NULL values in queries with practical examples and optimization tips. Feb 5, 2025 · This tip explores how to handle NULL values in SQL Server using the COALESCE() function using various queries and reviewing the results. . In this article, you will find out everything you need to know about coalesce and how to handle null values. By allowing users to substitute NULLs with meaningful values, COALESCE enhances the readability and robustness of SQL queries. Jan 10, 2017 · First, you are trying to insert an empty string '' to handle NULL values in the dojo column. The aggregate functions array_agg In this tutorial, you will learn how to use the PostgreSQL COALESCE() function to handle NULL in the database. You'll also need to know the column names. It's PostgreSQL and SQLite (and I'd like to not kill MySQL support either). NULL is not the same as an empty string. Oracle databases treat empty strings and NULL as the same. 2 days ago · The COALESCE(value, '') = '' expression simplifies checking for NULL/empty values in Postgres, replacing verbose multi-condition logic with a single, readable line. Flexible Value Handling: When combined with COALESCE, NULLIF allows for dynamic value substitution, offering a way to manage placeholder values and default fallbacks. The "" parameter will be resolved as a (column, or alias) identifier (an empty one, which i'm not sure if it's legal on its own or not). An empty string '' is something different then NULL - unless you are using Oracle which treats empty strings and NULL the same. Jun 15, 2017 · You have multiple errors in your query: trim() can only have 1 parameter, while coalesce() can have multiple & the empty string is ''. May 23, 2022 · This has got nothing to do with the COALESCE() operator, I just put it there to help with the example. How can I return an empty array when there are no tags? I have double checked that I don't have a null tag being returned. Nov 14, 2011 · @Martin Smith: I have just implemented your former solution which works well. For example, suppose we want a list of the product names with the brand name. Look at the following SELECT statement: Sep 22, 2023 · Discover the art of concatenating in PostgreSQL through our comprehensive guide. 1. Dec 17, 2013 · 3 I'm trying to replace some empty (NULL) fields, which I get as a result of my query, with any string I want. 4. "SELECT location. For further details on its usage, please read PostgreSQL COALESCE Function: Handling NULL Values Effectively. The best solution is update your code to display a blank or whatever you want when the field is NULL. It is the resulting value (which is a string) that needs casting to integer, per the original question. Otherwise you could cast the timestamp to TEXT Oct 3, 2024 · Between ISNULL () and COALESCE (), use ISNULL () if you know for sure that your code will run on Microsoft SQL Server but COALESCE () is better because it's standard and you can use it to replace NULL with empty String in any database like Oracle, MySQL, and PostgreSQL. First, it will return an empty (zero-element) array rather than NULL when the input string is of zero length. 1 versions of PostgreSQL. I have tried running this using a COALESCE(splitpart, '0') to no avail as it tried to read the empty field returned by the field index 2. Apr 3, 2025 · Discover how SQL Coalesce Empty String works in SQL Server. Learn how to combine fields, strings and columns effectively using various techniques and functions like || operator for optimized database management. Find out what then with MySQL. It represents missing, unknown, or inapplicable data. Jun 15, 2015 · I know I can write a if-then-else (CASE) statement in the query to check for this, but is there a nice simple function like COALESCE() for blank-but-not-null fields? Jun 6, 2024 · Learn how to select rows with NULL, empty strings, or both types of values. Learn how to replace NULL values with a default value through a clear example. Aug 30, 2024 · This tutorial explains how to replace null values with a string in a table in PostgreSQL, including an example. Currently I'm using: Sep 25, 2023 · COALESCE can be used with timestamps or dates in PostgreSQL to replace NULL values with strings, provided that you convert the column of type TIMESTAMP or DATE to string with a cast. I am using COALESCE. 3. Strings … HI Team, Kindly help to convert empty string to null in postgres. NULLIF () and COALESCE (): Perfect Partners NULLIF () and COALESCE () are complementary functions that work wonderfully together: NULLIF () converts specific values to NULL In Postgres: select 'test' || null returns null I was expecting it would otherwise return 'test'. Table of Contents PostgreSQL COALESCE function syntax PostgreSQL COALESCE example See more PostgreSQL COALESCE function syntax The syntax of the COALESCE function is as follows: Jul 23, 2020 · I was practicing SQL with PostgreSQL and I got stuck using COALESCE, maybe someone can tell me where I am going wrong. COALESCE functions with strings in the same way as it does with other data types. Jan 13, 2023 · In SQL, the COALESCE() function returns the first non-null value in an entry. city, '') = :city " Nov 13, 2025 · It should be noted that except for count, these functions return a null value when no rows are selected. May 9, 2024 · Discover the basics of PostgreSQL's COALESCE function, how it handles NULL values, and its application in SQL queries. "Display" is really up to the application displaying the data. Aug 19, 2025 · By using COALESCE, CASE expressions, or NULLIF, you can effectively handle NULL values in PostgreSQL. A CASE statement can be used to count the number of elements before passing them to the aggregation function, and return an empty string instead of NULL when the answer is zero. Jun 29, 2015 · However, if the object has no tags, Postgres returns this: [ null ] instead of an an empty array. Aug 11, 2020 · I've got the following table (nodes) in a PostgreSQL DB and I'm looking to extract either the http OR https information. hence there is a functionality mismatch in the output. how can i convert this empty string as null in config level. Concatenating NULL values with non-NULL characters results in that character in Oracle, but NULL in PostgreSQL. I would petition to keep the documentation as is and modify the function behaviour to be conformant to the documentation as it would be quite useful if COALESCE could also deal with empty strings. I'm trying to make the fastest COALESCE() that accepts two or more arguments, and returns the first non-null AND non-empty ("") value. Nov 13, 2025 · Note Although COALESCE, GREATEST, and LEAST are syntactically similar to functions, they are not ordinary functions, and thus cannot be used with explicit VARIADIC array arguments. Learn how to troubleshoot and fix 'NULL' string returns in PostgreSQL text queries with expert advice and relevant code examples. I have a table with four columns: title, height_cm, length_cm, and width_cm. Jun 7, 2017 · The technique of using empty strings instead of null values to trigger unique constraint validations works for all non-foreign-key fields. Note: There are two differences in the behavior of string_to_array from pre-9. id, arr Jul 20, 2025 · PostgreSQLの標準のCOALESCE関数は、引数の中から最初に現れるNULLではない値を返します。 しかし、空文字列はNULLではないので、COALESCE ('','Hello')とした場合、結果は''（空文字列）になってしまいます。 Jan 24, 2023 · In this post, we are going to understand what the COALESCE function is and how to use it in PostgreSQL. Can I use any of the above or does it have any performance issues or which one would you use What exactly a NULL value represents The flexible syntax of COALESCE Examples of tackling PostgreSQL and SQL Server NULLs Advanced patterns and use cases Performance tradeoffs to keep in mind So let’s get you armed with COALESCE and ready to wrangle those NULLs! Buckle up for some deeper SQL wisdom… What the NULL Represents Before we continue, it‘s important you understand what exactly a May 9, 2024 · Conclusion COALESCE is a practical, efficient solution for managing NULL values in PostgreSQL, offering simplicity and robustness in data handling. Perfect for beginners and experts alike! Aug 4, 2023 · Summary: in this tutorial, you will learn about the PostgreSQL COALESCE function that returns the first non-null argument. T Aug 28, 2023 · COALESCE Empty String in SQL Server The COALESCE function in SQL Server is utilized to return the first non-null expression among its arguments. Oct 29, 2012 · If I use array_agg to collect names, I get my names separated by commas, but in case there is a null value, that null is also taken as a name in the aggregate. You will learn how to apply this function in SELECT statement to handle null values effectively. but in oracle it is returning as null. Coalesce will take a large number of arguments. Oct 8, 2015 · Which due to the existence of potentially empty or null entries in the multiple rows returned from the second table, returns something like the following: server1;data;etc; ,1. Other PostgreSQL Functions To fully appreciate NULLIF (), it helps to understand how it relates to PostgreSQL‘s other NULL-handling functions. When working with PostgreSQL, handling NULL values is a common challenge. I Jan 4, 2024 · Dealing with Null Values Using CAST, you can also provide a fallback for NULL values with COALESCE: SELECT COALESCE(CAST(NULLIF(column_name, '') AS INTEGER), 0) FROM your_table; This code snippet will convert any empty strings in column_name to NULL and then replaces those NULLs with 0. Oct 26, 2023 · When navigating the realm of PostgreSQL, developers often stumble upon a myriad of functions, with the STRING_AGG () function being a frequently utilized, yet occasionally misunderstood, tool. Those empty fields are placed in a "timestamp without timezone" column. In this guide, we‘ll fully demystify coalesce in PostgreSQL. As others have pointed out, one solution would be to use current_timestamp as a placeholder. In PostgreSQL, the COALESCE () function is used to get the first non-null value among the specified arguments. It only ensures '0' (a string) is returned instead of NULL. Oct 20, 2016 · Let's introduce the COALESCE postgresql function. Which is '' in your example. Those methods lead to the same outcomes as ISNULL in other systems. However, in PostgreSQL, empty strings and NULL are different. The COALESCE function allows you to provide fallback functions in case of NULL values to ensure there's a value for any operation - or that you don't send NULLs back to the client. May 20, 2021 · Coalesce itself does not need casting. Oct 24, 2023 · To replace NULL values with an empty string, use COALESCE(column_name, ''). other than nullif function. Normal numeric Jul 20, 2025 · PostgreSQLの標準のCOALESCE関数は、引数の中から最初に現れるNULLではない値を返します。 しかし、空文字列はNULLではないので、COALESCE ('','Hello')とした場合、結果は''（空文字列）になってしまいます。 Dec 23, 2024 · Standardize Empty Values: NULLIF converts empty strings or specific placeholders to NULL, making data easier to work with. NULL indicates the absence of a value, and it can complicate arithmetic operations, comparisons, and function calls. This won't work, because empty string is not a valid timestamp. SQL IFNULL (), ISNULL (), COALESCE (), and NVL () Functions Look at the following "Products" table: Suppose that the "UnitsOnOrder" column is optional, and may contain NULL values. It fails any equality comparison. Mar 26, 2025 · The COALESCE function in PostgreSQL is designed to return the first non-null value from a list of expressions. Feb 5, 2014 · 1 As per your comment to replace empty string to some text, the simple solution is to use case statement like below. Aug 13, 2019 · Oracle treats empty string as NULL SQL> create table test ( col1 varchar (10), col2 varchar (10) ); Table created. I Those empty fields are placed in a 'timestamp without timezone' column. 2. Dec 19, 2017 · I am trying to deal with empty cells and get the data with empty cells filled with something like "Blank" string upon querying in PostgreSQL. Sep 23, 2013 · I have a Postgres table with a string column carrying numeric values. SELECT 1 FROM DUAL WHERE ( SELECT '' FROM dual) IS NULL In the above query SELECT '' FROM dual returns empty string in postgres. PostgreSQL provides a Jul 13, 2019 · My question might be postgreSQL related more than node-pg related, but I'm drawing a blank as to what could cause this issue. In PostgreSQL, the COALESCE () function and the IS NULL operator are used to find and replace the null values with some default values. Is this desired behavior? Seems weird that string concatenation with a null value would nullify May 20, 2016 · What is specific is whether the server treats a zero-length string as being equivalent to NULL, which determines whether concatenating a NULL yields a NULL or not. I need to convert these strings to numbers for math, but I need both NULL values as well as empty strings to be interpreted as Feb 1, 2024 · In this tutorial, you will learn about the PostgreSQL COALESCE() function that returns the first non-null argument. To query empty fields I have seen this answer: Postgresql, select empty fields (unfortunately I don't have enough reputation points to answer @wildplasser on that post, so here we go) Wildplasser's Select Coalesce(Other,Industry) Ind from registration The thing is that Other can be an empty string or NULL. CASE can return a value when the first non-null value is met in a sequence. Learn how to effectively use the COALESCE function in PostgreSQL to handle null values and return meaningful results. format This section describes functions and operators for examining and manipulating string values. So, as you can see in the examples below, the COALESCE statement with an empty string tries to use the next available value. Aug 1, 2023 · Learn how to handle null values with ease and efficiency using the versatile COALESCE() function in PostgreSQL, with practical examples and insights. How do I emulate the ISNULL() functionality ? Feb 1, 2016 · Here the objective is that if the Region column is Null then just replace that with '' (empty string). However, you can use is null or (less preferentially) coalesce(). com Jun 27, 2023 · Let’s explore the PostgreSQL coalesce function. You'll need to know the column name and do this for each column name. The aggregate docs say "The coalesce function can be used to substitute zero or an empty array for null when necessary". ” It is not 0, an empty string, or a single space, and it won’t cooperate with ordinary equality operators. It showcases the utility of these functions in data cleaning and management, particularly in complex grouping and summing operations. How do I get coalesce to work such that if Other is an empty string, Coalesce still returns Industry? Aug 7, 2023 · This example demonstrates how to handle null or empty string values in categorical data in PostgreSQL using COALESCE and CASE WHEN. Feb 10, 2025 · In PostgreSQL, the CASE statement can also be used as an alternative to IFNULL or COALESCE from other SQL dialects. nodes WHERE owne Feb 26, 2020 · COALESCE (value1, value2, ) | Returns the first value that is neither NULL nor empty string. If all arguments are NULL, it will return a NULL value. Important Points About PostgreSQL NULLIF () Function Short-Circuit Evaluation: NULLIF returns the first argument if it doesn't equal the second, avoiding further evaluation. If necessary, I can work around the NULL-issue (by filling in lots of empty strings), but I'd prefer something that works in both cases. By default, the psql terminal outputs the empty string whenever a null value is returned. Sep 2, 2023 · The original question asked for the best way to check if a given value is null or an empty string in Postgres SQL statements, where the value can be a long expression. Jan 19, 2023 · This article discusses the differences between how Oracle and PostgreSQL evaluate NULL characters and empty strings. Jan 14, 2012 · In MS SQL-Server, I can do: SELECT ISNULL(Field,'Empty') from Table But in PostgreSQL I get a syntax error. It evaluates the values of the entries one by one, ignores the null values, then returns the first value that is not null. This is how to apply it to strings: When use COALESCE, the proper syntax is as follows: Let’s see how to use COALESCE function in PostgreSQL: In this example, the default_value will be used in place of column_name if it is null. SQL> insert into test values ( '',null); 1 row created. Jan 4, 2024 · Introduction String concatenation is a fundamental operation in any database system, and PostgreSQL uses the double pipe || as a concatenation operator to merge strings together efficiently. foofoo), '{""}' AS foofoos Now how do you include array_agg ()? I'd like an array to return either way but array_agg doesn't accept COALESCE as an argument. You can't cast whitespace to a timestamp. This approach is more robust for NULL handling in PostgreSQL. Dec 23, 2024 · Learn how to use PostgreSQL’s COALESCE function to replace NULL values with default data. Jul 23, 2020 · I am trying to concatenate a number of columns and skip the column if column is NULL OR empty in postgres. Some of them can be null however, and in this case, node-pg returns them as null correctly, but I would Oct 1, 2018 · Postgresql COALESCE with String Literals does not work as expected Asked 6 years, 11 months ago Modified 6 years, 11 months ago Viewed 6k times May 24, 2022 · To avoid that, we can use the COALESCE() function to return an empty string (or a space) instead of a NULL. Type Casting in JOIN Clauses and WHERE Conditions Nov 13, 2025 · 9. FROM survey_data; NULLIF () vs. SELECT COALESCE(http,https) FROM oig. CASE WHEN COALESCE(TRIM(`field`), '') = '' THEN 'Blank ' ELSE 'Not Blank' END COALESCE will return the first non-null value it finds, used in this case it's saying if the field is null return an empty string. May 7, 2025 · _Official documentation: SQL Functions and Operators: COALESCE_ The COALESCE function in PostgreSQL returns the first non-null value in a list of expressions. I'm doing selects on a few columns which are all JSONB in postgres. Discover best practices for using COALESCE in data cleaning, default values, and complex SQL operations. For example : SELECT g. Oct 4, 2017 · Use COALESCE(city, '') - it will coerce NULL string to empty string "". The coalesce function can be used to substitute zero or an empty array for null when necessary. If you just want something quick and dirty that achieves something close to your goal, you can convert the whole row Nov 16, 2023 · This is where PostgreSQL‘s powerful coalesce function comes to the rescue! Coalesce allows you to gracefully handle NULL values by replacing them with a default value of your choice. If you have lots of cities and lots of queries to them, you can create an index on coalesced field to foster search. This guide seeks to demystify STRING_AGG (), taking you from its basics to its more advanced usage capabilities. Sep 15, 2020 · You have describe the behavior of a column that is NULL. id FROM location WHERE COALESCE(location. It's inevitable that some data in the database has no value. Generally COALESCE is most concise for PostgreSQL-style empty string handling, and DECODE (*VALUE*, NULL, '' for Oracle-style empty string handling. Well coalesce() returns the first non-null value. Another problem you have is that you are incorrectly using to_char to format your timestamp data. It works in PostgreSQL, SQL server, and MySQL. May 23, 2022 · Handling empty strings (”) with all NULL-compatible operators or expressions while migrating from Oracle to PostgreSQL is vital to achieve overall functional acceptance on the converted code and have a holistic impact. Aug 13, 2021 · 0 Have a code select coalesce(ex. Learn best practices to handle NULLs & empty strings efficiently. When we have numerous expressions or values and want to choose the first one that isn’t null, we can use it frequently. Feb 18, 2024 · The COALESCE function in PostgreSQL is used to return the function’s first parameter that is not null. Jul 15, 2025 · The COALESCE function is a powerful tool for handling NULL values in PostgreSQL. MktShrExclude,'') <> 'true' from Market ex; column MktShrExclude is Boolean type but getting an error invalid input syntax for type boolean: "" Please Help. My query looks like this : SELECT t_id, a_date, c_date, Feb 18, 2024 · COALESCE functions with strings in the same way as it does with other data types. This feature is particularly useful when dealing with incomplete datasets, as it allows developers to provide fallback values seamlessly. Apr 16, 2015 · When using COALESCE, an e mpty string is treated the same as a NULL value. Apr 5, 2025 · Understanding NULL in PostgreSQL PostgreSQL’s NULL means “no value. Second, if the delimiter string is NULL, the function splits the input into individual characters, rather than returning NULL as before. How can I accomplish this? I have tried split_part() and cast as int. I use PGAdmin 3, and by default that shows NULLs as "blank", though you can configure it to show something else like <NULL> for NULLs instead. When dealing with empty strings (”) and null values, COALESCE sees an empty string as a legitimate value, therefore if it’s the first non-null argument, it will return an empty string. This tutorial explores the versatile Aug 19, 2017 · Etc. To convert a column into text, you can use column_name::TEXT or CAST(column_name AS TEXT). I'm using this: CREATE OR REPLACE FUNCTION coalescenonempty( See full list on sqlshack. Oracle reads empty strings as NULLs, while PostgreSQL treats them as empty. Jun 9, 2025 · A simple guide for using the SQL COALESCE function in PostgreSQL. Instead, PostgreSQL follows three-valued logic: any comparison involving NULL yields UNKNOWN, which in turn behaves like FALSE in WHERE clauses. I've wrapped the field in a trim to remove any leading or trailing whitespaces in case someone has a value of all spaces to ignore. However, split_part(version, "-", 2) will return what looks like an empty string. Here is an description from Sneha Gohil on Oracle to PostgreSQL Migration: The Empty String Trap. I'll try this too. You‘ll learn: What coalesce is and how it works Real-world examples and use cases for coalesce How to use coalesce in your PostgreSQL queries How How to coalesce an empty/null value that is part of Concact string in Postgres? Asked 5 years, 2 months ago Modified 5 years, 2 months ago Viewed 2k times What is best way to check if value is null or empty string in Postgres sql statements? Value can be long expression so it is preferable that it is written only once in check. Coalesce will return the first non null value in the list. 4,,,; The coalesce statement is one of the most powerful functions in PostgreSQL, because it ensures that your calculations and results are not filled with null values, which can cause errors in your applications. Understand the syntax, examples, and practical use cases for cleaner queries. So I tried to use COALESCE function, but no result (I got error: invalid input syntax for timestamp: "any_string": Jun 22, 2025 · Mastering COALESCE in PostgreSQL The dreaded NULL Introduction In the world of databases, NULL is a necessary evil. For example: I put coalesce around the field and get empty string array, but wouldn't this prevent an array of names when there could be an array of them? COALESCE(fp. Thus: SELECT COALESCE (null, null, 5) returns 5, while. xtkmhzls orpap xfwgvy odm fcof evycl qscdcip uogy lzvf pui tsbkz dssc xpxihuxk dmpdgaz nptbm