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https://dev.mysql.com/doc/refman/8.4/en/string-functions.html
mysql> SELECT CONCAT_WS(',', 'First name', 'Second name', 'Last Name'); -> 'First name,Second name,Last Name' mysql> SELECT CONCAT_WS(',', 'First name', NULL, 'Last Name'); -> 'First name,Last Name' CONCAT_WS() does not skip empty strings. The ...
https://dev.mysql.com/doc/refman/8.4/en/partitioning-handling-nulls.html
Partitioning in MySQL does nothing to disallow NULL as the value of a partitioning expression, whether it is a column value or the value of a user-supplied expression. Even though it is permitted to use NULL as the value of an expression that must ...We can verify this behavior by examining the effects on the file system of creating a table partitioned by HASH and populating it with a record containing appropriate ...
https://dev.mysql.com/doc/refman/8.4/en/working-with-null.html
A common error when working with NULL is to assume that it is not possible to insert a zero or an empty string into a column defined as NOT NULL, but this is not the case. The NULL value can be surprising until you get used to it. Conceptually, ...
https://dev.mysql.com/doc/refman/8.4/en/problems-with-null.html
The concept of the NULL value is a common source of confusion for newcomers to SQL, who often think that NULL is the same thing as an empty string ''. For example, the following statements are completely different: mysql> INSERT INTO my_table ...In ...When reading data with LOAD DATA, empty or missing columns are updated with ...
https://dev.mysql.com/doc/refman/8.4/en/is-null-optimization.html
MySQL can perform the same optimization on col_name IS NULL that it can use for col_name = constant_value. For example, MySQL can use indexes and ranges to search for NULL with IS NULL. This optimization does not occur in cases when the column ...
https://dev.mysql.com/doc/internals/en/null-bitmap.html
The binary protocol sends NULL values as bits inside a bitmap instead of a full byte as the ProtocolText::ResultsetRow does. If many NULL values are sent, it is more efficient than the old way. The NULL-bitmap needs enough space to store a possible ...Caution For the Binary Protocol Resultset Row the num-fields and the field-pos need to add a offset ...
https://dev.mysql.com/doc/refman/8.4/en/null-values.html
Be aware that the NULL value is different from values such as 0 for numeric types or the empty string for string types. The NULL value means “no data.” NULL can be written in any lettercase. For sorting with ORDER BY, NULL values sort before ...
https://dev.mysql.com/doc/internals/en/optimizer-early-nulls-filtering.html
Here the early NULLs filtering for ref (or eq_ref) access is applied. We make the following inference: (tblY.key_partN = tblX.column) => (tblX.column IS NOT NULL) The original equality can be checked only after we've read the current rows of both ...
https://dev.mysql.com/doc/connectors/en/connector-net-programming-datetime-null.html
As such, when assigning values from a query to a DateTime variable, you must first check whether the value is in fact NULL.
https://dev.mysql.com/doc/connector-net/en/connector-net-programming-datetime-null.html
As such, when assigning values from a query to a DateTime variable, you must first check whether the value is in fact NULL.