From 239c84fc620d76e98547a8387e1aaa6d7d995b79 Mon Sep 17 00:00:00 2001
From: drh <>
Date: Fri, 19 Feb 2021 09:09:07 +0000
Subject: [PATCH] Give a better error message on DROP COLUMN when attempting to
 drop the last column of a table.

FossilOrigin-Name: 5e1f362bc3e53c60f9e6f771346d10c6e6a6cb3ff1eec5608101f9c5d6d2a5a4
---
 manifest               | 14 +++++++-------
 manifest.uuid          |  2 +-
 src/alter.c            |  6 ++++++
 test/alterdropcol.test |  4 +---
 4 files changed, 15 insertions(+), 11 deletions(-)

diff --git a/manifest b/manifest
index adef7e5a09..646161d8d2 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Add\sa\sNEVER()\sto\san\sunreachable\sbranch\sin\sthe\sDROP\sCOLUMN\slogic.
-D 2021-02-19T02:30:02.782
+C Give\sa\sbetter\serror\smessage\son\sDROP\sCOLUMN\swhen\sattempting\sto\sdrop\nthe\slast\scolumn\sof\sa\stable.
+D 2021-02-19T09:09:07.189
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -475,7 +475,7 @@ F spec.template 86a4a43b99ebb3e75e6b9a735d5fd293a24e90ca
 F sqlite.pc.in 42b7bf0d02e08b9e77734a47798d1a55a9e0716b
 F sqlite3.1 fc7ad8990fc8409983309bb80de8c811a7506786
 F sqlite3.pc.in 48fed132e7cb71ab676105d2a4dc77127d8c1f3a
-F src/alter.c b2a3c89c5bcf5251cfb786e608381ef506d71a9f1c375e277124cc924e4546f9
+F src/alter.c ae5ff195830c9fb15869067340ab3e619fb41332907c75f0fd0c8756e4a3826d
 F src/analyze.c 01c6c6765cb4d40b473b71d85535093730770bb186f2f473abac25f07fcdee5c
 F src/attach.c e80162a47411f296bea550ed8fafd730481f4aa71e89ece23ba9c957eed15d4a
 F src/auth.c 08954fdc4cc2da5264ba5b75cfd90b67a6fc7d1710a02ccf917c38eadec77853
@@ -647,7 +647,7 @@ F test/alter4.test dfd6086faf461b27ca2d2999848dcd207edf23352fc1592d0005c0844f3f0
 F test/alterauth.test 63442ba61ceb0c1eeb63aac1f4f5cebfa509d352276059d27106ae256bafc959
 F test/alterauth2.test 794ac5cef251819fe364b4fe20f12f86e9c5d68070513c7fd26c17cb244c89af
 F test/altercol.test 1d6a6fe698b81e626baea4881f5717f9bc53d7d07f1cd23ee7ad1b931f117ddf
-F test/alterdropcol.test f4fb3a02a7274740769506f2af2eb8cc60aac26a148b71564b79fe3a19acae3b
+F test/alterdropcol.test baad37ff9b07078ea02dcc33dbfb82bde655f3eee5c453e218f69501c36f02ba
 F test/alterlegacy.test f38c6d06cda39e1f7b955bbce57f2e3ef5b7cb566d3d1234502093e228c15811
 F test/altermalloc.test 167a47de41b5c638f5f5c6efb59784002b196fff70f98d9b4ed3cd74a3fb80c9
 F test/altermalloc2.test fa7b1c1139ea39b8dec407cf1feb032ca8e0076bd429574969b619175ad0174b
@@ -1902,7 +1902,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 9bb720e6590482bc9c2fbb273738808209e9651710dbee7572b0348cadf87e68
-R c0fbd4f44b1d4f87e911757503e8d30c
+P 963f498ae64cf7530fb7a405fa476c411ad66523f62f5eefa5a16596cd19a481
+R aa22eacb2d5994361fbd57544a6b9a8f
 U drh
-Z 525012fbf3fca5430284eed456ca18e8
+Z 3143b8a85ae4a74a1f1f600bf54bbab2
diff --git a/manifest.uuid b/manifest.uuid
index 870b42977f..bde579b620 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-963f498ae64cf7530fb7a405fa476c411ad66523f62f5eefa5a16596cd19a481
\ No newline at end of file
+5e1f362bc3e53c60f9e6f771346d10c6e6a6cb3ff1eec5608101f9c5d6d2a5a4
\ No newline at end of file
diff --git a/src/alter.c b/src/alter.c
index a4caf71598..cb25f98078 100644
--- a/src/alter.c
+++ b/src/alter.c
@@ -1880,6 +1880,12 @@ void sqlite3AlterDropColumn(Parse *pParse, SrcList *pSrc, Token *pName){
     goto exit_drop_column;
   }
 
+  /* Do not allow the number of columns to go to zero */
+  if( pTab->nCol<=1 ){
+    sqlite3ErrorMsg(pParse, "cannot drop column \"%s\": no other columns exist",zCol);
+    goto exit_drop_column;
+  }
+
   /* Edit the sqlite_schema table */
   iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
   assert( iDb>=0 );
diff --git a/test/alterdropcol.test b/test/alterdropcol.test
index 7edb05f4b9..1087f66328 100644
--- a/test/alterdropcol.test
+++ b/test/alterdropcol.test
@@ -72,7 +72,7 @@ do_execsql_test 1.7.2 {
 
 do_catchsql_test 1.7.3 {
   ALTER TABLE t1 DROP COLUMN a;
-} {1 {error in table t1 after drop column: near ")": syntax error}}
+} {1 {cannot drop column "a": no other columns exist}}
 
 
 do_catchsql_test 1.8 {
@@ -256,5 +256,3 @@ do_catchsql_test 5.5.2 {
 } {1 {error in trigger tr: no such column: new.z}}
 
 finish_test
-
-
-- 
2.47.2