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Q&A Why would excluding records by creating a temporary table of their primary keys be faster than simply excluding by value?

I have two tables with millions of records. Every so often I need to join them and exclude just a handful of records where a bit(1) column is set to 1 instead of 0. I can do it with either, WHERE ...

2 answers  ·  posted 4y ago by Charlie Brumbaugh‭  ·  edited 4y ago by Alexei‭

#5: Post edited by user avatar Alexei‭ · 2020-10-19T05:16:37Z (about 4 years ago)
added relevant tags
  • I have two tables with millions of records. Every so often I need to join them and exclude just a handful of records where a bit(1) column is set to 1 instead of 0.
  • I can do it with either,
  • ```sql
  • WHERE is_excluded !=1
  • ```
  • or
  • ```sql
  • WHERE example_table.pk NOT IN
  • (
  • SELECT pk FROM(
  • SELECT pk FROM
  • example_table
  • WHERE is_excluded =1)
  • AS t)
  • ```
  • For example
  • ```
  • UPDATE example_table
  • SET textfield = 'X'
  • WHERE textfield = 'Y'
  • and pk not in (SELECT pk FROM (SELECT pk FROM example_table WHERE do_not_touch =1)as t) ;
  • ```
  • is faster than
  • ```
  • UPDATE example_table
  • SET textfield = 'X'
  • WHERE textfield = 'Y'
  • and do_not_touch !=1
  • ```
  • The second way is sometimes way faster, even though it takes much longer to write out.
  • Why would the second way be faster?
  • I have two tables with millions of records. Every so often I need to join them and exclude just a handful of records where a bit(1) column is set to 1 instead of 0.
  • I can do it with either,
  • ```sql
  • WHERE is_excluded !=1
  • ```
  • or
  • ```sql
  • WHERE example_table.pk NOT IN
  • (
  • SELECT pk FROM(
  • SELECT pk FROM
  • example_table
  • WHERE is_excluded =1)
  • AS t)
  • ```
  • For example
  • ```
  • UPDATE example_table
  • SET textfield = 'X'
  • WHERE textfield = 'Y'
  • and pk not in (SELECT pk FROM (SELECT pk FROM example_table WHERE do_not_touch =1)as t) ;
  • ```
  • is faster than
  • ```
  • UPDATE example_table
  • SET textfield = 'X'
  • WHERE textfield = 'Y'
  • and do_not_touch !=1
  • ```
  • The second way is sometimes way faster, even though it takes much longer to write out.
  • Why would the second way be faster?
#4: Post edited by user avatar Charlie Brumbaugh‭ · 2020-08-07T18:24:28Z (about 4 years ago)
  • I have two tables with millions of records. Every so often I need to join them and exclude just a handful of records where a bit(1) column is set to 1 instead of 0.
  • I can do it with either,
  • ```sql
  • WHERE is_excluded !=1
  • ```
  • or
  • ```sql
  • WHERE example_table.pk NOT IN
  • (
  • SELECT pk FROM(
  • SELECT pk FROM
  • example_table
  • WHERE is_excluded =1)
  • AS t)
  • ```
  • The second way is sometimes way faster, even though it takes much longer to write out.
  • Why would the second way be faster?
  • I have two tables with millions of records. Every so often I need to join them and exclude just a handful of records where a bit(1) column is set to 1 instead of 0.
  • I can do it with either,
  • ```sql
  • WHERE is_excluded !=1
  • ```
  • or
  • ```sql
  • WHERE example_table.pk NOT IN
  • (
  • SELECT pk FROM(
  • SELECT pk FROM
  • example_table
  • WHERE is_excluded =1)
  • AS t)
  • ```
  • For example
  • ```
  • UPDATE example_table
  • SET textfield = 'X'
  • WHERE textfield = 'Y'
  • and pk not in (SELECT pk FROM (SELECT pk FROM example_table WHERE do_not_touch =1)as t) ;
  • ```
  • is faster than
  • ```
  • UPDATE example_table
  • SET textfield = 'X'
  • WHERE textfield = 'Y'
  • and do_not_touch !=1
  • ```
  • The second way is sometimes way faster, even though it takes much longer to write out.
  • Why would the second way be faster?
#3: Post edited by user avatar ArtOfCode‭ · 2020-08-07T16:35:47Z (about 4 years ago)
tags, syntax highlighting hints
  • I have two tables with millions of records. Every so often I need to join them and exclude just a handful of records where a bit(1) column is set to 1 instead of 0.
  • I can do it with either,
  • ```
  • WHERE is_excluded !=1
  • ```
  • or
  • ```
  • WHERE example_table.pk NOT IN
  • (
  • SELECT pk FROM(
  • SELECT pk FROM
  • example_table
  • WHERE is_excluded =1)
  • AS t)
  • ```
  • The second way is sometimes way faster, even though it takes much longer to write out.
  • Why would the second way be faster?
  • I have two tables with millions of records. Every so often I need to join them and exclude just a handful of records where a bit(1) column is set to 1 instead of 0.
  • I can do it with either,
  • ```sql
  • WHERE is_excluded !=1
  • ```
  • or
  • ```sql
  • WHERE example_table.pk NOT IN
  • (
  • SELECT pk FROM(
  • SELECT pk FROM
  • example_table
  • WHERE is_excluded =1)
  • AS t)
  • ```
  • The second way is sometimes way faster, even though it takes much longer to write out.
  • Why would the second way be faster?
#2: Post edited by user avatar Charlie Brumbaugh‭ · 2020-08-07T15:24:27Z (about 4 years ago)
  • I have two tables with millions of records. Every so often I need to join them and exclude just handful of records where a bit(1) column is set to 1 instead of 0.
  • I can do it with either,
  • ```
  • WHERE is_excluded !=1
  • ```
  • or
  • ```
  • WHERE example_table.pk NOT IN
  • (
  • SELECT pk FROM(
  • SELECT pk FROM
  • example_table
  • WHERE is_excluded =1)
  • AS t)
  • ```
  • The second way is sometimes way faster, even though it takes much longer to write out.
  • Why would the second way be faster?
  • I have two tables with millions of records. Every so often I need to join them and exclude just a handful of records where a bit(1) column is set to 1 instead of 0.
  • I can do it with either,
  • ```
  • WHERE is_excluded !=1
  • ```
  • or
  • ```
  • WHERE example_table.pk NOT IN
  • (
  • SELECT pk FROM(
  • SELECT pk FROM
  • example_table
  • WHERE is_excluded =1)
  • AS t)
  • ```
  • The second way is sometimes way faster, even though it takes much longer to write out.
  • Why would the second way be faster?
#1: Initial revision by user avatar Charlie Brumbaugh‭ · 2020-08-07T15:13:08Z (about 4 years ago)
Why would excluding records by creating a temporary table of their primary keys be faster than simply excluding by value?
I have two tables with millions of records. Every so often I need to join them and  exclude just handful of records where a bit(1) column is set to 1 instead of 0.

I can do it with either,

```
WHERE is_excluded !=1
```

or

```
WHERE example_table.pk NOT IN
(
  SELECT pk FROM(
    SELECT pk FROM
    example_table
    WHERE is_excluded =1) 
AS t)
```

The second way is sometimes way faster, even though it takes much longer to write out.

Why would the second way be faster?