In MySQL, the COALESCE() operator returns the first non-NULL value in the list, or NULL if there are no non-NULL values.
Tag: operators
SQL Server COALESCE() Explained
In SQL Server, the COALESCE() expression returns its first non-null argument.
The way it works is, we pass a list of arguments to the expression, it evaluates the arguments in order and returns the current value of the first expression that initially doesn’t evaluate to NULL.
Fix Error: “SELECTs to the left and right of UNION do not have the same number of result columns” in SQLite
If you’re getting “Error: in prepare, SELECTs to the left and right of UNION do not have the same number of result columns…” in when trying to use the UNION operator in SQLite, it’s because one of the SELECT statements is returning more columns than the other.
SQLite ->> Operator
In SQLite, the ->> operator extracts a subcomponent from a JSON document and returns an SQL representation of that subcomponent.
The ->> operator was first introduced in SQLite version 3.38.0 (released on 22 February 2022).
SQLite -> Operator
In SQLite, the -> operator extracts a subcomponent from a JSON document and returns a JSON representation of that subcomponent.
The -> operator was first introduced in SQLite version 3.38.0 (released on 22 February 2022).
Fix “ERROR 1222 (21000): The used SELECT statements have a different number of columns” when using UNION in MariaDB
When using the UNION operator in MariaDB, you may encounter the following error: “ERROR 1222 (21000): The used SELECT statements have a different number of columns”.
This error occurs when the number of columns returned by each SELECT statement is different.
The way to fix this is to ensure that both SELECT statements return the same number of columns.
SQLite Introduces the -> and ->> Operators for Extracting JSON Subcomponents
Starting with SQLite version 3.38.0 (released on 22 February 2022), we can now use the -> and ->> operators to extract subcomponents of JSON documents.
The aim with these operators is to be compatible with the equivalent MySQL and PostgreSQL operators.
Continue readingFix “ERROR 1222 (21000): The used SELECT statements have a different number of columns” when using UNION in MySQL
If you’re getting “ERROR 1222 (21000): The used SELECT statements have a different number of columns” when using the UNION clause in a MySQL query, it’s probably because the number of columns returned by each SELECT statement is different.
Fix “ERROR 1250 (42000): Table ‘…’ from one of the SELECTs cannot be used in global ORDER clause” when using UNION in MySQL
If you’re getting an error that reads “ERROR 1250 (42000): Table ‘…’ from one of the SELECTs cannot be used in global ORDER clause” when using the UNION clause in a MySQL query, it’s probably because you’re qualifying a column name with its table name.
This doesn’t work in MySQL.
To fix this issue, either remove the table name or use a column alias.
Continue readingFix “ERROR 1054 (42S22): Unknown column ‘…’ in ‘order clause'” when using UNION in MySQL
If you’re getting error “1054 (42S22): Unknown column ‘…’ in ‘order clause'” when using the UNION clause in MySQL, it could be because you’re trying to reference an aliased column by its column name.