How to skip null values ​​in string concatenation in sql

When concatenating strings in SQL, you can skip null values ​​through the following methods: COALESCE() function: Returns the first non-NULL value. IFNULL() function: If the first parameter is not NULL, returns the first parameter, otherwise returns the second parameter. ISNULL() function: Checks whether a value is NULL and returns TRUE or FALSE accordingly.

SQL string splicing skips null values

When splicing strings in SQL, if a null value is encountered value, usually returns NULL, thus affecting the splicing result. To skip null values, you can use the following method:

COALESCE() function:

COALESCE() The function returns the first non-NULL The value of Returns a complete name string containing first and last name.

IFNULL() function:

IFNULL() If the first parameter is not NULL, the function returns the first parameter, otherwise Return the second parameter, the syntax is as follows:

<code class="sql">COALESCE(value1, value2, ...)</code>

For example:

<code class="sql">SELECT COALESCE(name, '') || ' ' || COALESCE(surname, '') AS full_name
FROM table_name;</code>

This query has the same effect as using the

COALESCE()

function.

ISNULL() function:

ISNULL() Function checks whether a value is NULL. If it is NULL, it returns TRUE, otherwise it returns FALSE, the syntax is as follows:

<code class="sql">IFNULL(value1, value2)</code>

For example:

<code class="sql">SELECT IFNULL(name, '') || ' ' || IFNULL(surname, '') AS full_name
FROM table_name;</code>

This query uses the

CASE

statement. If surname is NULL, an empty string is returned. Otherwise, spaces and

surname

are returned.

Note: When using these methods, ensure that the replacement value is compatible with the string type to be concatenated.

For some database systems, there may be other specific functions to handle null value splicing.

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