# Converting legacy sql build scripts into models

**URL:** <https://discourse.getdbt.com/t/converting-legacy-sql-build-scripts-into-models/2845>\
**Category:** Archive\
**Created:** [August 3, 2021, 10:13pm UTC](https://discourse.getdbt.com/t/converting-legacy-sql-build-scripts-into-models/2845 "2021-08-03T22:13:41Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![ericpp](https://avatars.discourse-cdn.com/v4/letter/e/dbc845/32.png) [@ericpp](https://discourse.getdbt.com/u/ericpp)\
**Post date:** [August 3, 2021, 10:13pm UTC](https://discourse.getdbt.com/t/converting-legacy-sql-build-scripts-into-models/2845/1 "2021-08-03T22:13:41Z")

</div>

Hello,

I’m currently working to convert legacy sql build scripts into dbt models. Most of the scripts start out with a simple `CREATE TABLE xxx AS SELECT <columns> FROM table` statement and then run subsequent `UPDATE` statements to make changes to the values of the table.

I’m currently handling this in dbt by packaging each update into its own CTE, e.g.:

```auto
WITH source AS (
  SELECT * FROM ref('source')
),
fix_col1_value AS (
  SELECT
    {{ dbt_utils.star(ref('source'), except=["col1"]) }},
    CASE
      WHEN othercol = 'val' THEN 'newval'
      ELSE col1
    END AS col1
  FROM
    source
),
fix_col2_value AS (
  SELECT
    {{ dbt_utils.star(ref('source'), except=["col2"]) }},
    CASE
      WHEN someothercol = 'val' THEN 'newval2'
      ELSE col2
    END AS col2
  FROM
    fix_col1_value
),
...
final AS (
  SELECT * FROM fix_colX_value
)
SELECT * FROM final

```

Is this a good approach for handling something like this? I do like that the individual updates from the old script are still separated out as CTEs rather than being jumbled together into one `SELECT` statement.

The code itself feels a bit long with a lot of repeated `{{ dbt_utils.star() }}` calls. It also feels potentially error prone if someone adds a new CTE and forgets to update the chain of CTEs.

Thanks,  
Eric