Question

我有许多数据库，外键（非正式）字段名和主键字段名对于以下代码中可见的样本是相同的。

CREATE TABLE Customer(
   CustomerId int PRIMARY,
   CustomerName varchar(200),
...
)
CREATE TABLE Invoice(
      InvoiceID int PRIMARY KEY,
      InvoiceType int ,
      CustomerID int)
CREATE TABLE InvoiceDet(
      InvoiceDetId int PRIMARY KEY,
      InvoiceId int ...)

我想要一个程序（或脚本）来读取我的表，列并创建外键引用。应该生成关系：Customer.CustomerId<=>Invoice.CustomerID和 InvoiceDet.InvoiceId<=>Invoice.InvoiceId

Answer 1

这是一个巨大的任务，用于创建此类自动脚本，尤其是对于您提到的所有数据库。您应该考虑聘请一些具有perl / python知识的优秀DBA为您做这件事。

使用最少量的检查（密钥中的列数和列的类型不进行交叉检查），以下可能是PostgreSQL的concept proof：

WITH colnames(oid,colnum,colname) AS (
    SELECT a.attrelid AS oid, a.attnum AS colnum, a.attname AS colname
      FROM pg_attribute a WHERE a.attnum > 0 AND NOT a.attisdropped),
pkcols(oid,colnum) AS (
    SELECT c.conrelid AS oid, unnest(c.conkey)
      FROM pg_constraint c
     WHERE contype = 'p'),
pks(oid,colnum,colname) AS (
    SELECT pkc.oid, pkc.colnum, cn.colname
      FROM pkcols pkc
      JOIN colnames cn ON pkc.oid = cn.oid AND pkc.colnum = cn.colnum),
pktabs AS (
    SELECT t.oid AS oid, n.nspname AS sname, t.relname AS tname,
           pks.colnum AS colnum, pks.colname AS colname
      FROM pg_class t
      JOIN pg_namespace n ON n.oid = t.relnamespace
      JOIN pks ON pks.oid = t.oid
     WHERE t.relkind = 'r'),
coltabs AS (
    SELECT t.oid AS oid, n.nspname AS sname, t.relname AS tname,
           cn.colnum AS colnum, cn.colname AS colname
      FROM pg_class t
      JOIN pg_namespace n ON n.oid = t.relnamespace
      JOIN colnames cn ON cn.oid = t.oid
     WHERE t.relkind = 'r')
SELECT 'ALTER TABLE '||quote_ident(ct.sname)||'.'||quote_ident(ct.tname)||
       ' ADD FOREIGN KEY ('||string_agg(quote_ident(pk.colname),',')||
       ') REFERENCES '||
       quote_ident(pk.sname)||'.'||quote_ident(pk.tname)||' ('||
       string_agg(quote_ident(pk.colname),',')||');'
  FROM pktabs pk
  JOIN coltabs ct ON pk.oid != ct.oid AND pk.colname = ct.colname
 GROUP BY pk.sname,pk.tname,ct.sname,ct.tname;

在各种SQL语法中创建自动关系

1 个答案: