What is the Best way to Perform Bulk insert in oracle ? - oracle

Question

With this, I mean Inserting millions of records in tables. I know how to insert data using loops but for inserting millions of data it won't be a good approach.
I have two tables
CREATE TABLE test1
(
col1 NUMBER,
valu VARCHAR2(30),
created_Date DATE,
CONSTRAINT pk_test1 PRIMARY KEY (col1)
)
/
CREATE TABLE test2
(
col2 NUMBER,
fk_col1 NUMBER,
valu VARCHAR2(30),
modified_Date DATE,
CONSTRAINT pk_test2 PRIMARY KEY (col2),
FOREIGN KEY (fk_col1) REFERENCES test1(col1)
)
/
Please suggest a way to insert some dummy records upto 1 million without loops.

Answer 1

As a fairly simplistic approach, which may be enough for you based on your comments, you can generate dummy data using a hierarchical query. Here I'm using bind variables to control how many are created, and to make some of the logic slightly clearer, but you could use literals instead.
First, parent rows:
var parent_rows number;
var avg_children_per_parent number;
exec :parent_rows := 5;
exec :avg_children_per_parent := 3;
-- create dummy parent rows
insert into test1 (col1, valu, created_date)
select level,
dbms_random.string('a', dbms_random.value(1, 30)),
trunc(sysdate) - dbms_random.value(1, 365)
from dual
connect by level <= :parent_rows;
which might generate rows like:
COL1 VALU CREATED_DA
---------- ------------------------------ ----------
1 rYzJBVI 2016-11-14
2 KmSWXfZJ 2017-01-20
3 dFSTvVsYrCqVm 2016-07-19
4 iaHNv 2016-11-08
5 AvAxDiWepPeONGNQYA 2017-01-20
Then child rows, which a random fk_col1 in the range generated for the parent:
-- create dummy child rows
insert into test2 (col2, fk_col1, valu, modified_date)
select level,
round(dbms_random.value(1, :parent_rows)),
dbms_random.string('a', dbms_random.value(1, 30)),
trunc(sysdate) - dbms_random.value(1, 365)
from dual
connect by level <= :parent_rows * :avg_children_per_parent;
which might generate:
select * from test2;
COL2 FK_COL1 VALU MODIFIED_D
---------- ---------- ------------------------------ ----------
1 2 AqRUtekaopFQdCWBSA 2016-06-30
2 4 QEczvejfTrwFw 2016-09-23
3 4 heWMjFshkPZNyNWVQG 2017-02-19
4 4 EYybXtlaFHkAYeknhCBTBMusGAkx 2016-03-18
5 4 ZNdJBQxKKARlnExluZWkHMgoKY 2016-06-21
6 3 meASktCpcuyi 2016-10-01
7 4 FKgmf 2016-09-13
8 3 JZhk 2016-06-01
9 2 VCcKdlLnchrjctJrMXNb 2016-05-01
10 5 ddL 2016-11-27
11 4 wbX 2016-04-20
12 1 bTfa 2016-06-11
13 4 QP 2016-08-25
14 3 RgmIahPL 2016-03-04
15 2 vhinLUmwLwZjczYdrPbQvJxU 2016-12-05
where the number of children varies for each parent:
select fk_col1, count(*) from test2 group by fk_col1 order by fk_col1;
FK_COL1 COUNT(*)
---------- ----------
1 1
2 3
3 3
4 7
5 1
To insert a million rows instead, just change the bind variables.
If you needed more of a relationship between the children and parents, e.g. so the modified date is always after the created date, you can modify the query; for example:
insert into test2 (col2, fk_col1, valu, modified_date)
select *
from (
select level,
round(dbms_random.value(1, :parent_rows)) as fk_col1,
dbms_random.string('a', dbms_random.value(1, 30)),
trunc(sysdate) - dbms_random.value(1, 365) as modified_date
from dual
connect by level <= :parent_rows * :avg_children_per_parent
) t2
where not exists (
select null from test1 t1
where t1.col1 = t2.fk_col1 and t1.created_date > t2.modified_date
);
You may also want non-midnight times (I set everything to midnight via the trunc() call, based on the column name being 'date' not 'datetime'), or some column values null; so this might just be a starting point for you.