docs(notes): add ibm-db2 table column entry

Author: lzwjava

Diff for: notes/2025-04-11-ibm-db2-table-column-en.md

@@ -0,0 +1,148 @@
+---
+title: Exact Table and Column in IBM Db2
+lang: en
+layout: post
+audio: false
+translated: false
+generated: true
+---
+
+Yes — this extra info absolutely helps! When DB2 gives error messages like:
+
+```
+SQLCODE = -407, SQLSTATE = 23502
+TBSPACEID=2, TABLEID=266, COLNO=0
+```
+
+These internal identifiers (`TBSPACEID`, `TABLEID`, `COLNO`) point to **the exact table and column** where the error occurred — but they’re not human-readable directly. You need to query the DB2 **system catalog** to decode them.
+
+---
+
+### 🔍 How to find the column from TBSPACEID, TABLEID, and COLNO
+
+You can use this query:
+
+```sql
+SELECT
+    tabschema,
+    tabname,
+    colname,
+    colno
+FROM
+    syscat.columns
+WHERE
+    tbspaceid = 2 AND
+    tableid = 266 AND
+    colno = 0;
+```
+
+> 💡 If `tbspaceid` and `tableid` aren’t directly in `syscat.columns` (depends on DB2 version), you can use this instead:
+
+```sql
+SELECT
+    c.tabschema,
+    c.tabname,
+    c.colname,
+    c.colno
+FROM
+    syscat.columns c
+JOIN
+    sysibm.systables t
+    ON c.tabschema = t.creator AND c.tabname = t.name
+WHERE
+    t.tbspaceid = 2 AND
+    t.tableid = 266 AND
+    c.colno = 0;
+```
+
+---
+
+### 🧠 Then What?
+
+Once you know the `colname`, go back to your insert/update statement and check:
+- Are you setting a value for that column?
+- Is that value `NULL`?
+- Is the column defined as `NOT NULL` in the schema?
+
+Add a proper value or modify your insert/update to ensure the column gets a non-NULL value.
+
+---
+
+Want to dig in together? If you can share the table name or insert query, I can help pinpoint the fix quickly.
+
+---
+
+The error you're seeing:
+
+```
+com.ibm.db2.SqlIntegrityConstraintViolationException: 
+Assignment of a NULL value to a NOT NULL column is not allowed. 
+SQLCODE = -407, SQLSTATE = 23502
+```
+
+### 🔍 What it means:
+This happens when you're trying to insert or update a row in a DB2 table, and **a column that is defined as `NOT NULL` is being assigned a NULL value**.
+
+---
+
+### ✅ How to fix it:
+
+#### 1. **Identify the column**
+The key part is: **which column is NULL** when it shouldn’t be?
+
+Sometimes DB2 error messages include the column name, but if it doesn’t, here are ways to find it:
+
+---
+
+#### 🔎 Option 1: Enable DB2 diagnostics / logs
+If you can enable **DB2 tracing or diagnostic logs**, they may show the exact SQL and which column is problematic.
+
+---
+
+#### 🔎 Option 2: Look at the table DDL
+Run:
+```sql
+DESCRIBE TABLE your_table_name
+```
+Look for columns with `NOT NULL`.
+
+Then check your **insert/update query** and see which of those columns **are missing or have NULLs**.
+
+---
+
+#### 🔎 Option 3: Add debug output to your code
+If you're inserting data via Java or another language, **print/log the data** before executing the insert. Look for missing or `null` values.
+
+---
+
+#### 🔎 Option 4: Narrow it down with a test insert
+Manually try inserting values into the table, starting with only the NOT NULL fields:
+```sql
+INSERT INTO your_table_name (col1, col2, col3)
+VALUES ('val1', 'val2', NULL) -- Try each one until it breaks
+```
+This helps you pinpoint the problematic column.
+
+---
+
+### 🛠️ Example Fix:
+Suppose your table has a column `username VARCHAR(100) NOT NULL`, and you try:
+```sql
+INSERT INTO users (email) VALUES ('[email protected]')
+```
+This fails because `username` was not given and is `NOT NULL`.
+
+You fix it by doing:
+```sql
+INSERT INTO users (username, email) VALUES ('user1', '[email protected]')
+```
+
+---
+
+### 🧠 Pro Tip:
+If this is part of a Java + JDBC code, make sure **you’re setting all required fields**, especially the ones that are `NOT NULL`.
+
+---
+
+Would you like help reviewing a specific insert/update query or Java code snippet? I can help spot the exact cause.
+