摘要:
PG新增自定义函数 举例。添加完自定义系统函数之后需要initdb才生效。 1. 添加proc脚本 vim src/include/catalog/pg_proc.dat 新增UDF set_new_transaction_id #function to set new transaction ID 阅读全文
摘要:
SQL JOINS Relation algebra Natural join (⋈) The result of the natural join is the set of all combinations of tuples in R and S that are equal on their 阅读全文