是否有一种方法使用SQL列出给定表的所有外键?我知道表名/模式,我可以把它插入。
当前回答
这个查询也适用于组合键:
select c.constraint_name
, x.table_schema as schema_name
, x.table_name
, x.column_name
, y.table_schema as foreign_schema_name
, y.table_name as foreign_table_name
, y.column_name as foreign_column_name
from information_schema.referential_constraints c
join information_schema.key_column_usage x
on x.constraint_name = c.constraint_name
join information_schema.key_column_usage y
on y.ordinal_position = x.position_in_unique_constraint
and y.constraint_name = c.unique_constraint_name
order by c.constraint_name, x.ordinal_position
其他回答
您可以通过information_schema表来实现这一点。例如:
SELECT
tc.table_schema,
tc.constraint_name,
tc.table_name,
kcu.column_name,
ccu.table_schema AS foreign_table_schema,
ccu.table_name AS foreign_table_name,
ccu.column_name AS foreign_column_name
FROM
information_schema.table_constraints AS tc
JOIN information_schema.key_column_usage AS kcu
ON tc.constraint_name = kcu.constraint_name
AND tc.table_schema = kcu.table_schema
JOIN information_schema.constraint_column_usage AS ccu
ON ccu.constraint_name = tc.constraint_name
AND ccu.table_schema = tc.table_schema
WHERE tc.constraint_type = 'FOREIGN KEY' AND tc.table_name='mytable';
PSQL就是这样做的,如果你用:
psql -E
它将准确地显示执行了哪些查询。在查找外键的情况下,它是:
SELECT conname,
pg_catalog.pg_get_constraintdef(r.oid, true) as condef
FROM pg_catalog.pg_constraint r
WHERE r.conrelid = '16485' AND r.contype = 'f' ORDER BY 1
在这种情况下,16485是我正在寻找的表的oid -你可以通过将你的表名转换为regclass来获得它:
WHERE r.conrelid = 'mytable'::regclass
如果表名不是唯一的(或者是搜索路径中的第一个),则对表名进行模式限定:
WHERE r.conrelid = 'myschema.mytable'::regclass
另一种方式:
WITH foreign_keys AS (
SELECT
conname,
conrelid,
confrelid,
unnest(conkey) AS conkey,
unnest(confkey) AS confkey
FROM pg_constraint
WHERE contype = 'f' -- AND confrelid::regclass = 'your_table'::regclass
)
-- if confrelid, conname pair shows up more than once then it is multicolumn foreign key
SELECT fk.conname as constraint_name,
fk.confrelid::regclass as referenced_table, af.attname as pkcol,
fk.conrelid::regclass as referencing_table, a.attname as fkcol
FROM foreign_keys fk
JOIN pg_attribute af ON af.attnum = fk.confkey AND af.attrelid = fk.confrelid
JOIN pg_attribute a ON a.attnum = conkey AND a.attrelid = fk.conrelid
ORDER BY fk.confrelid, fk.conname
;
最快的验证直接在bash答案完全基于这个答案
IFS='' read -r -d '' sql_code << EOF_SQL_CODE
SELECT
o.oid
, o.conname AS constraint_name
, (SELECT nspname FROM pg_namespace WHERE oid=m.relnamespace) AS source_schema
, m.relname AS source_table
, (SELECT a.attname FROM pg_attribute a
WHERE a.attrelid = m.oid AND a.attnum = o.conkey[1] AND a.attisdropped = false) AS source_column
, (SELECT nspname FROM pg_namespace
WHERE oid=f.relnamespace) AS target_schema
, f.relname AS target_table
, (SELECT a.attname FROM pg_attribute a
WHERE a.attrelid = f.oid AND a.attnum = o.confkey[1] AND a.attisdropped = false) AS target_column
, ROW_NUMBER () OVER (ORDER BY o.oid) as rowid
FROM pg_constraint o
LEFT JOIN pg_class f ON f.oid = o.confrelid
LEFT JOIN pg_class m ON m.oid = o.conrelid
WHERE 1=1
AND o.contype = 'f'
AND o.conrelid IN (SELECT oid FROM pg_class c WHERE c.relkind = 'r')
EOF_SQL_CODE
psql -d my_db -c "$sql_code"
SELECT
conrelid::regclass AS table_from,
conname,
pg_get_constraintdef(oid) as condef
FROM pg_catalog.pg_constraint r
也适用于所有约束条件。例如,使用pysql:
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