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Add warning about varchar(max) #688

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Merged
merged 4 commits into from
Oct 9, 2025
Merged

Add warning about varchar(max) #688

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baf2d00
Add warning about varchar(max)
mkincaid-bw Oct 8, 2025
3601c64
Fix copy/paste issue
mkincaid-bw Oct 8, 2025
0f3ffd2
Implement Claude's suggestions.
mkincaid-bw Oct 8, 2025
592fe93
Updated comment. Also fixed example statements
mkincaid-bw Oct 9, 2025
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20 changes: 12 additions & 8 deletions docs/contributing/code-style/sql.md
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Original file line number Diff line number Diff line change
Expand Up @@ -462,10 +462,8 @@ WHERE
[Column] IS NULL
GO

ALTER TABLE
[dbo].[Column]
ALTER COLUMN
[Column] INT NOT NULL
ALTER TABLE [dbo].[Table]
ALTER COLUMN [Column] INT NOT NULL
GO
```

Expand All @@ -474,14 +472,20 @@ This is better:
```sql
IF COL_LENGTH('[dbo].[Table]', 'Column' IS NULL
BEGIN
ALTER TABLE
[dbo].[Column]
ADD
[Column] INT NOT NULL CONSTRAINT DF_Table_Column DEFAULT 0
ALTER TABLE [dbo].[Table]
ADD [Column] INT NOT NULL CONSTRAINT DF_Table_Column DEFAULT 0
END
GO
```

:::warning Do not use defaults for string columns

Default values should only be used for integral types (`BIT`, `TINYINT`, `SMALLINT`, `INT`,
`BIGINT`). Do not provide default values for string columns (`VARCHAR`, `NVARCHAR`, or their `MAX`
variants), as this can lead to unnecessary storage overhead and performance issues.

:::

#### Changing a column data type

You must wrap the `ALTER TABLE` statement in a conditional block, so that subsequent runs of the
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