Summary of MySQL's commonly used concatenation statements

SELECT DISTINCT
  CONCAT(
    'User: \'',
    USER,
    '\'@\'',
    HOST,
    '\';'
  ) AS QUERY
FROM
  mysql.USER;
# When ' appears in the concatenated string, you need to use the \ escape character

SELECT
  CONCAT(
    'DROP table ',
    TABLE_NAME,
    ';'
  )
FROM
  information_schema. TABLES
WHERE
  TABLE_SCHEMA = 'test';

SELECT
  concat('KILL ', id, ';')
FROM
  information_schema. PROCESSLIST
WHERE
  STATE LIKE 'Creating sort index';

SELECT
  CONCAT(
    'create database ',
    '`',
  SCHEMA_NAME,
  '`',
  ' DEFAULT CHARACTER SET ',
  DEFAULT_CHARACTER_SET_NAME,
    ';'
  ) AS CreateDatabaseQuery
FROM
  information_schema.SCHEMATA
WHERE
  SCHEMA_NAME NOT IN (
    'information_schema',
    'performance_schema',
    'mysql',
    'sys'
  );

SELECT
  CONCAT(
    'create user \'',
  user,
  '\'@\'',
  Host,
  '\''
  ' IDENTIFIED BY PASSWORD \'',
  authentication_string,
    '\';'
  ) AS CreateUserQuery
FROM
  mysql.`user`
WHERE
  `User` NOT IN (
    'root',
    'mysql.session',
    'mysql.sys'
  );
# There is a password string. You can directly create a user with the same password as this instance by executing it in other instances

#!/bin/bash 
#Function export user privileges 

pwd=yourpass 
expgrants() 
{ 
 mysql -B -u'root' -p${pwd} -N $@ -e "SELECT CONCAT( 'SHOW GRANTS FOR ''', user, '''@''', host, ''';' ) AS query FROM mysql.user" | \
 mysql -u'root' -p${pwd} $@ | \
 sed 's/\(GRANT .*\)/\1;/;s/^\(Grants for .*\)/-- \1 /;/--/{x;p;x;}' 
} 

expgrants > /tmp/grants.sql
echo "flush privileges;" >> /tmp/grants.sql

SELECT t.TABLE_SCHEMA,
    t.TABLE_NAME,
    t.TABLE_ROWS,
    concat(round(t.DATA_LENGTH / 1024 / 1024, 2), 'M') AS size,
    t.INDEX_LENGTH,
    concat(round(t.DATA_FREE / 1024 / 1024, 2), 'M') AS datafree
FROM information_schema.tables t
WHERE t.TABLE_SCHEMA = 'test' order by DATA_LENGTH desc;

#Find a table without a primary key in a certain librarySELECT
table_schema,
table_name
FROM
  information_schema.TABLES
WHERE
  table_schema = 'test'
AND TABLE_NAME NOT IN (
  SELECT
    table_name
  FROM
    information_schema.table_constraints
  JOIN information_schema.key_column_usage k USING (
    constraint_name,
    table_schema,
    table_name
  )
  WHERE
    t.constraint_type = 'PRIMARY KEY'
  AND t.table_schema = 'test'
);

#Search for tables without primary keys except system librariesSELECT
  t1.table_schema,
  t1.table_name
FROM
  information_schema. TABLES t1
LEFT OUTER JOIN information_schema.TABLE_CONSTRAINTS t2 ON t1.table_schema = t2.TABLE_SCHEMA
AND t1.table_name = t2.TABLE_NAME
AND t2.CONSTRAINT_NAME IN ('PRIMARY')
WHERE
  t2.table_name IS NULL
AND t1.TABLE_SCHEMA NOT IN (
  'information_schema',
  'performance_schema',
  'mysql',
  'sys'
) ;