# `zAddField_Proc` (procedure)


- **Type:** PROCEDURE
- **Deterministic:** NO
- **SQL data access:** CONTAINS SQL

## Parameters

| # | Mode | Name | Type |
|---|---|---|---|
| 1 | IN | `sColumnName` | `varchar(100)` |
| 2 | IN | `sTableName` | `varchar(100)` |
| 3 | IN | `sType` | `varchar(100)` |
| 4 | IN | `sDefault` | `varchar(100)` |
| 5 | IN | `sIsNull` | `varchar(100)` |
| 6 | IN | `sComment` | `varchar(255)` |

## Body

_Body is not pre-cached. To inspect: `mysql --defaults-file=~/.my.cnf -e 'SHOW CREATE PROCEDURE `zAddField_Proc`'`._

## Narrative

**Business context:** Maintenance / migration helper (lower-case `z`-prefixed). Idempotent column-adder used by Flyway scripts and several DB routines to grow a business table by one new column without failing when the column already exists — `ALTER TABLE ... ADD COLUMN` only fires when `information_schema.COLUMNS` shows the column is missing.

**What it does:** Reads the current schema via `SELECT DATABASE()`, lower-cases `sType`. Guards with `IF NOT EXISTS (SELECT * FROM information_schema.COLUMNS WHERE COLUMN_NAME=sColumnName AND TABLE_SCHEMA=sTableSchema AND TABLE_NAME=sTableName)`. When `sDefault` is `''` it picks a type-appropriate default (`''`, `0`, `0.000000`, `b'0'`, `now()`); when non-empty it formats the value for the type. Builds `ALTER TABLE \`<tbl>\` ADD COLUMN \`<col>\` <type> <default> <isnull> <comment>` and runs it through `PREPARE`/`EXECUTE`. Skips entirely when `sTableName='salsalesorderslave'` (hardcoded carve-out). Also inserts the table name into a `aaa(bb)` audit-stub row before the ALTER — likely leftover from prior debugging.

**Invocation:** Used by other DB routines: `sp_do_initsysjurisdiction`, `sp_int_dbSet`, `Sp_sYzfy_JN`. Extensively called by Flyway migrations under `xly-src/xlyEntry/src/main/resources/flyway/V*.sql`, `xlyFace/.../V*.sql`, `xlyPlc/.../V*.sql` plus customer upgrade scripts in `script/标版/upgrade/` (e.g. `V2.0.21__20240125_addColumn.sql`, `20220105-2751-保存、删除调过程/zAddFieldProc.sql`). Fires whenever the application boot path runs Flyway or a maintainer applies a manual upgrade SQL. The `INSERT into aaa(bb)` debug write will fail if table `aaa` is absent — flag for cleanup.