#String concatenation concat(s1,s2); concatenate the strings in last_name and first_name in the table select concat(last_name,first_name) as name from employees; #Only last_name will be modified, not first_name SELECT first_name,last_name AS f FROM employees; # Separate the two columns with a comma and name them out_put SELECT CONCAT(`last_name`,',',`phone_number`) AS out_put FROM employees; #ifnull determines whether it is empty. If it is empty, it will be displayed as 0 instead of null, and the column name will be displayed as the result SELECT IFNULL(commission_pct,0) AS result FROM employees; Content extension: String concatenation 1.1 The CONCAT(s1, s2, ...) function returns the string generated by concatenating the parameters, one or more contents to be concatenated. If any one of them is NULL, the return value is NULL. SELECT CONCAT('Current time:',NOW()); -- Output result: Current time: 2019-01-17 11:27:58 1.2 CONCAT_WS(x,s1,s2,...) function Returns a string consisting of multiple strings concatenated together, with an x between each string. SELECT CONCAT_WS(';','pan_junbiao's blog','KevinPan','pan_junbiao'); -- Output: pan_junbiao's blog;KevinPan;pan_junbiao I hope the above content can help everyone. Thank you for your support of 123WORDPRESS.COM. You may also be interested in:
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