Para automatizar el proceso de copia de seguridad de una de mis bases de datos MySQL, me gustaría comparar la estructura de dos tablas (versión actual frente a versión anterior).

¿Se te ocurre una consulta que pueda comparar dos tablas?

Aquí hay algunas tablas de ejemplo que puede comparar.

CREATE TABLE product_today
(
  pname VARCHAR(150),
  price int,
  PRIMARY KEY (pname)
);

CREATE TABLE product_yesterday
(
  pname VARCHAR(150),
  price int,
  PRIMARY KEY (pname)
);

CREATE TABLE product_2days_back
(
  pname VARCHAR(15),
  price int,
  PRIMARY KEY (pname)
);

Las dos primeras tablas tienen estructuras idénticas. El último es diferente. Solo necesito saber si dos tablas tienen estructuras diferentes o no. No estoy interesado en cómo difieren.

DOS TABLAS EN LA BASE DE DATOS ACTUAL

Si desea saber si dos tablas son diferentes, ejecute esto

SELECT IF(COUNT(1)>0,'Differences','No Differences') Comparison FROM
(
    SELECT
        column_name,ordinal_position,
        data_type,column_type,COUNT(1) rowcount
    FROM information_schema.columns
    WHERE table_schema=DATABASE()
    AND table_name IN ('product_today','product_yesterday')
    GROUP BY
        column_name,ordinal_position,
        data_type,column_type
    HAVING COUNT(1)=1
) A;

Si realmente necesita ver las diferencias, ejecute esto

SELECT column_name,ordinal_position,data_type,column_type FROM
(
    SELECT
        column_name,ordinal_position,
        data_type,column_type,COUNT(1) rowcount
    FROM information_schema.columns
    WHERE table_schema=DATABASE()
    AND table_name IN ('product_today','product_yesterday')
    GROUP BY
        column_name,ordinal_position,
        data_type,column_type
    HAVING COUNT(1)=1
) A;

DOS TABLAS EN UNA BASE DE DATOS ESPECÍFICA

Si desea saber si dos tablas son diferentes en la base de datos mydb, ejecute esto

SELECT IF(COUNT(1)>0,'Differences','No Differences') Comparison FROM
(
    SELECT
        column_name,ordinal_position,
        data_type,column_type,COUNT(1) rowcount
    FROM information_schema.columns
    WHERE table_schema='mydb'
    AND table_name IN ('product_today','product_yesterday')
    GROUP BY
        column_name,ordinal_position,
        data_type,column_type
    HAVING COUNT(1)=1
) A;

Si realmente necesita ver las diferencias, ejecute esto

SELECT column_name,ordinal_position,data_type,column_type FROM
(
    SELECT
        column_name,ordinal_position,
        data_type,column_type,COUNT(1) rowcount
    FROM information_schema.columns
    WHERE table_schema='mydb'
    AND table_name IN ('product_today','product_yesterday')
    GROUP BY
        column_name,ordinal_position,
        data_type,column_type
    HAVING COUNT(1)=1
) A;

DOS TABLAS EN DOS BASES DE DATOS DIFERENTES

Si quieres saber si db1.tb1y db2.tb2son diferentes, ejecuta esto

SELECT IF(COUNT(1)>0,'Differences','No Differences') Comparison FROM
(
    SELECT
        column_name,ordinal_position,
        data_type,column_type,COUNT(1) rowcount
    FROM information_schema.columns
    WHERE
    (
        (table_schema='db1' AND table_name='tb1') OR
        (table_schema='db2' AND table_name='tb2')
    )
    AND table_name IN ('product_today','product_yesterday')
    GROUP BY
        column_name,ordinal_position,
        data_type,column_type
    HAVING COUNT(1)=1
) A;

Si realmente necesita ver las diferencias, ejecute esto

SELECT column_name,ordinal_position,data_type,column_type FROM
(
    SELECT
        column_name,ordinal_position,
        data_type,column_type,COUNT(1) rowcount
    FROM information_schema.columns
    WHERE
    (
        (table_schema='db1' AND table_name='tb1') OR
        (table_schema='db2' AND table_name='tb2')
    )
    AND table_name IN ('product_today','product_yesterday')
    GROUP BY
        column_name,ordinal_position,
        data_type,column_type
    HAVING COUNT(1)=1
) A;

DARLE UNA OPORTUNIDAD !!!

Puede comparar la suma de comprobación de salida de SHOW CREATE TABLE product_today

# mysql -NBe "SHOW CREATE TABLE sakila.actor"| sed -r 's/AUTO_INCREMENT=[0-9]+/AUTO_INCREMENT=XXX/g' | md5sum
# 1bc0d72b294d1a93ce01b9a2331111cc  -

Ampliando la respuesta de RolandoMySQLDBA:

Para ver también el nombre de la tabla, consulte esto:

SELECT table_name, column_name,ordinal_position,data_type,column_type FROM
(
    SELECT
        table_name, column_name,ordinal_position,
        data_type,column_type,COUNT(1) rowcount
    FROM information_schema.columns
    WHERE table_schema=DATABASE()
    AND table_name IN ('table_1','table_2')
    GROUP BY
        column_name,ordinal_position,
        data_type,column_type
    HAVING COUNT(1)=1
) A;

Eche un vistazo a la tabla de columnas en el esquema de información: el campo tipo_columna. Eso le permitirá comparar estructuras de tablas.

Mi mejor manera de comparar 2 bases de datos (DB1, DB2): solo tablas / vistas, restricciones y claves externas no están incluidas. En mi caso, siempre uso el siguiente SQL para comparar PRODUCTION con UAT o UAT con DEV.

DB DIFF (comparar tablas / vistas)

select x.* from (
SELECT a.table_name, a.column_name,
    max(IF(b.TS='S1',b.ordinal_position,null)) as S1_ordinal_position,
    max(IF(b.TS='S2',b.ordinal_position,null)) as S2_ordinal_position,
    max(IF(b.TS='S1',b.data_type       ,null)) as S1_data_type,
    max(IF(b.TS='S2',b.data_type       ,null)) as S2_data_type,
    max(IF(b.TS='S1',b.column_type     ,null)) as S1_column_type,
    max(IF(b.TS='S2',b.column_type     ,null)) as S2_column_type
FROM
(SELECT DISTINCT table_name, column_name
 FROM information_schema.columns
 WHERE table_schema IN ('DB1','DB2')
) a
INNER JOIN
(SELECT IF(table_schema='DB1','S1','S2') as TS,
    table_schema,table_name,column_name,ordinal_position,data_type,column_type
 FROM information_schema.columns
 WHERE table_schema IN ('DB1','DB2')
) b
on (a.table_name = b.table_name and a.column_name = b.column_name)
group by a.table_name, a.column_name
) x
where x.S1_ordinal_position != x.S2_ordinal_position or x.S1_ordinal_position is null or x.S2_ordinal_position is null
or    x.S1_data_type        != x.S2_data_type
or    x.S1_column_type      != x.S2_column_type
ORDER BY x.table_name;

para todos los cambios en la estructura de tablas de dos bases de datos:

SELECT table_schema, table_name, column_name,ordinal_position,data_type,column_type FROM (
    SELECT
        table_schema, table_name, column_name,ordinal_position,
        data_type,column_type,COUNT(1) rowcount
    FROM information_schema.columns
    WHERE table_schema IN ('database1', 'database2')
    GROUP BY
        column_name,ordinal_position,
        data_type,column_type
    HAVING COUNT(1)=1 ) A;

Ref .: de RolandoMySQLDBA ans