SQLite目标
我想从一个连接(或一系列连接/子查询)创建一个新表。我希望新表保留原始表中的数据类型以及唯一索引。
另外,我想重命名过程中的一些列。要在SQLite中执行此操作,我的印象是我需要执行以下步骤:
- 将联接表创建为临时表
- 使用所需的列名,数据类型和索引创建一个空的新表
- 将临时表插入新表。
问题:有没有更好或更简洁的方法来完成这项任务?
上述过程的代码示例:
--create joined table as tmp
DROP TABLE if exists tmp;
CREATE TABLE tmp AS
SELECT
individual_contributions.cmte_id,
cmte_pty_affiliation,
name,
employer,
transaction_dt,
transaction_amt,
file_num,
cand_id,
sub_id
FROM individual_contributions LEFT JOIN committee_master
ON individual_contributions.cmte_id=committee_master.cmte_id
WHERE employer LIKE "Goldman Sachs"
GROUP BY sub_id;
--create new table with desired specs
DROP TABLE if exists cm_indiv;
CREATE TABLE cm_indiv (
cmte_id TEXT NOT NULL,
cmte_pty_affiliation TEXT,
contributor_name TEXT,
contributor_employer TEXT,
contributor_transaction_dt TEXT,
cand_id TEXT,
transaction_amt TEXT,
file_num NUMERIC,
sub_id NUMERIC NOT NULL
);
CREATE UNIQUE INDEX idx_cm_indiv ON cm_indiv (sub_id);
--insert joined table into new table
INSERT INTO cm_indiv (
cmte_id,
cmte_pty_affiliation,
contributor_name,
contributor_employer,
contributor_transaction_dt,
cand_id,
transaction_amt,
file_num,
sub_id
)
SELECT
cmte_id,
cmte_pty_affiliation,
name,
employer,
transaction_dt,
cand_id,
transaction_amt,
file_num,
sub_id
FROM tmp;
这个CTAS使用SQL Fiddle(SQLite-WebSQL)为我工作。因此,在创建表时,请在select语句中使用首选列名,如下所示。
create table tbl( id int);
insert into tbl values (1);
create table new_tbl
as
select id as new_id
from tbl;
select new_id from new_tbl;
Result:
new_id
1
首先创建新表,然后直接插入连接的数据:
CREATE TABLE cm_indiv ( cmte_id TEXT NOT NULL, ...);
INSERT INTO cm_indiv(...) SELECT ... FROM ... JOIN ...;
CREATE INDEX ...;