[Err] 1290

error message ：[Err] 1290 - The MySQL server is running with the --secure-file-priv option so it cannot execute this statement
scene ： Set the database table to txt The format is exported to windows Local error . [SQL]select * from tt into outfile 'C:\\tt.txt';
reason ：mysql No permission to operate local folder
solve ：1. Modify the permissions     2. The export folder is modified to C:/ProgramData/MySQL/MySQL Server x.x/Uploads/, You have permission to this folder by default .select * from tt into outfile 'C:\\ProgramData\\MySQL\\MySQL Server 8.0\\Uploads\\tt.txt';

[Err] 1267

error message ：[Err] 1267 - Illegal mix of collations (utf8mb4_0900_ai_ci,IMPLICIT) and (utf8mb4_unicode_ci,IMPLICIT) for operation '='
scene ： When performing an association query on two tables, an error appears .[SQL]select * from t1 INNER JOIN t2 on t1.id = t2.id;
reason ： An error is reported because the sorting rules of the two associated fields are inconsistent
solve ： Unify the character sorting rules of two association tables ( Fields of all text types in the table, such as varchar、text、… The collation will automatically follow the table ).alter table Table name convert to character set utf8mb4 COLLATE utf8mb4_0900_ai_ci;[set The newly set character set and the sorting rules of the character set are shown later , Can be used for other ]