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RyanLamanskyRyanLamansky
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Implemented MERGE INTO <view>.
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‎CLAUDE.md‎

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@@ -184,7 +184,7 @@ Per-feature deep-dives live under `docs/claude/`. Each entry below is a trigger:
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- `RANGE BETWEEN <N> PRECEDING/FOLLOWING` numeric-offset — Msg 4194, matching real SQL Server's licensed-feature rejection. `ROWS` numeric-offset ships. Default frame with ORDER BY is `RANGE UNBOUNDED PRECEDING TO CURRENT ROW`; without it, whole partition. LAST_VALUE matches real SQL Server's default-frame semantic.
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- Recursive-part feature restrictions (Msg 460 / 461 / 462 / 467 / 465) — silently accepted with possibly-incorrect semantics. Apps that exercise these hit rejection on real SQL Server too.
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- `LEN(ntext)` raising Msg 8116; legacy `READTEXT` / `WRITETEXT` / `UPDATETEXT`.
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- **MERGE gaps**: `MERGE INTO <view>` — confirmed against real SQL Server 2025 as a real feature (single-base updatable view, source via `VALUES` / SELECT / bare-table all work). Three related shapes initially flagged as gaps turned out to be invalid on real SQL Server too (Msg 156 at parse): `USING (WITH cte AS …)`, `MERGE` inside a CTE body, and multi-statement `WHEN` bodies. CTE-precedes-MERGE bare-name form (`WITH cte AS (…) MERGE … USING cte ON …`) ships.
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- **MERGE gaps**: CTE-precedes-MERGE bare-name form (`WITH cte AS (…) MERGE … USING cte ON …`) and `MERGE INTO <updatable view>` both ship; the latter has full parity with the UPDATE / INSERT / DELETE-through-view shapes — visibility filter scopes the target row set, `WITH CHECK OPTION` enforced on inserts / updates (Msg 550), view-column rename / reorder translates through `View.BaseColumnOrdinals`, INSTEAD OF INSERT / UPDATE / DELETE triggers replace the heap-write path per action. `MERGE … OUTPUT` through a view raises `NotSupportedException` (matches existing pattern; view-column projection through `INSERTED` / `DELETED` deferred). Three related shapes initially flagged as gaps turned out to be invalid on real SQL Server too (Msg 156 at parse): `USING (WITH cte AS …)`, `MERGE` inside a CTE body, and multi-statement `WHEN` bodies.
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- `UNIQUE` on a *non-persisted* computed column (PK/UNIQUE on `PERSISTED` ships). Msg 4936 determinism gate for PERSISTED computed columns also not enforced.
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- Heap allocation tracking (flat page list, no IAM/PFS).
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- **Table-variable named constraints / foreign keys** — Msg 102 (matches real SQL Server's grammar restriction inside `DECLARE @t TABLE`). Multi-variable DECLARE with a table variable, mixed scalar+table DECLARE, and `SET IDENTITY_INSERT @t ON` also reject. Column features (IDENTITY / UNIQUE / inline + table-level CHECK / computed / rowversion) all ship — see [`table-variables.md`](docs/claude/table-variables.md).

‎SqlServerSimulator.Tests/MergeViewTests.cs‎

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using static Microsoft.VisualStudio.TestTools.UnitTesting.Assert;
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namespace SqlServerSimulator;
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/// <summary>
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/// MERGE INTO updatable view — full parity with the
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/// UPDATE / INSERT / DELETE-through-view shapes: view-column lookups
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/// translate through <c>BaseColumnOrdinals</c>, visibility filters scope
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/// the target row set, <c>WITH CHECK OPTION</c> is enforced on
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/// inserts/updates, and INSTEAD OF triggers replace the heap-write path
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/// per action. Probed against real SQL Server 2025 (2026-05-19).
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/// </summary>
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[TestClass]
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public sealed class MergeViewTests
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{
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[TestMethod]
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public void SimpleView_NotMatchedInsert_LandsInBase()
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{
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var sim = new Simulation();
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sim.ExecuteBatches(
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"create table base_t (id int primary key, v int)",
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"create view v_base as select id, v from base_t",
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"""
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merge into v_base using (values(1,10),(2,20)) src(id, v) on v_base.id = src.id
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when not matched then insert (id, v) values (src.id, src.v);
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""");
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AreEqual(2, sim.ExecuteScalar("select count(*) from base_t"));
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AreEqual(10, sim.ExecuteScalar("select v from base_t where id = 1"));
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}
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[TestMethod]
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public void SimpleView_MatchedUpdate_LandsInBase()
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{
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var sim = new Simulation();
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sim.ExecuteBatches(
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"create table base_t (id int primary key, v int); insert base_t values (1, 0)",
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"create view v_base as select id, v from base_t",
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"""
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merge into v_base using (values(1, 99)) src(id, v) on v_base.id = src.id
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when matched then update set v = src.v;
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""");
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AreEqual(99, sim.ExecuteScalar("select v from base_t where id = 1"));
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}
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[TestMethod]
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public void SimpleView_NotMatchedBySourceDelete_RemovesBaseRows()
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{
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var sim = new Simulation();
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sim.ExecuteBatches(
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"create table base_t (id int primary key, v int); insert base_t values (1,1),(2,2),(3,3)",
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"create view v_base as select id, v from base_t",
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"""
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merge into v_base using (values(1,11)) src(id, v) on v_base.id = src.id
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when matched then update set v = src.v
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when not matched by source then delete;
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""");
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AreEqual(1, sim.ExecuteScalar("select count(*) from base_t"));
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AreEqual(11, sim.ExecuteScalar("select v from base_t where id = 1"));
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}
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[TestMethod]
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public void RenamedColumns_ViewColumnNamesAreUsedInMerge()
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{
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var sim = new Simulation();
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sim.ExecuteBatches(
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"create table base_t (id int primary key, v int)",
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"create view v_renamed as select id as pk, v as score from base_t",
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"""
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merge into v_renamed using (values(1, 100), (2, 200)) src(pk, score) on v_renamed.pk = src.pk
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when not matched then insert (pk, score) values (src.pk, src.score);
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""");
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AreEqual(100, sim.ExecuteScalar("select v from base_t where id = 1"));
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AreEqual(200, sim.ExecuteScalar("select v from base_t where id = 2"));
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}
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[TestMethod]
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public void ReorderedColumns_BaseColumnOrdinalsTranslate()
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{
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var sim = new Simulation();
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sim.ExecuteBatches(
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"create table base_t (id int primary key, v int, label varchar(20))",
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"create view v_reordered as select label, id, v from base_t",
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"""
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merge into v_reordered using (values('foo', 1, 10)) src(label, id, v) on v_reordered.id = src.id
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when not matched then insert (label, id, v) values (src.label, src.id, src.v);
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""");
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AreEqual("foo", sim.ExecuteScalar("select label from base_t where id = 1"));
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AreEqual(10, sim.ExecuteScalar("select v from base_t where id = 1"));
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}
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[TestMethod]
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public void VisibilityFilter_HidesNonMatchingTargetRows()
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{
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// Base row id=2 has active=0, so the view filter excludes it. The
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// MERGE source has both id=1 and id=2; id=2 is invisible to the view
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// so the NMBT branch triggers an INSERT — which conflicts with the
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// hidden row's PK, raising Msg 2627.
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var sim = new Simulation();
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sim.ExecuteBatches(
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"create table base_t (id int primary key, v int, active bit); insert base_t values (1, 100, 1), (2, 200, 0)",
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"create view v_active as select id, v from base_t where active = 1");
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var ex = sim.AssertSqlError("""
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merge into v_active using (values(1, 11), (2, 22)) src(id, v) on v_active.id = src.id
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when matched then update set v = src.v
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when not matched then insert (id, v) values (src.id, src.v);
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""", 2627);
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Assert.Contains("PRIMARY KEY", ex.Message);
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}
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[TestMethod]
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public void VisibilityFilter_OnlyVisibleRowsParticipateInMatched()
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{
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// Same setup, but a source that only hits the visible row → no
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// conflict; UPDATE applies to id=1 and leaves id=2 untouched.
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var sim = new Simulation();
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sim.ExecuteBatches(
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"create table base_t (id int primary key, v int, active bit); insert base_t values (1, 100, 1), (2, 200, 0)",
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"create view v_active as select id, v from base_t where active = 1",
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"""
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merge into v_active using (values(1, 11)) src(id, v) on v_active.id = src.id
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when matched then update set v = src.v;
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""");
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AreEqual(11, sim.ExecuteScalar("select v from base_t where id = 1"));
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AreEqual(200, sim.ExecuteScalar("select v from base_t where id = 2"));
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}
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[TestMethod]
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public void CheckOption_InsertViolation_RaisesMsg550()
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{
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// CHECK OPTION on v_pos requires v > 0; INSERT of v = -5 violates.
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var sim = new Simulation();
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sim.ExecuteBatches(
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"create table base_t (id int primary key, v int)",
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"create view v_pos as select id, v from base_t where v > 0 with check option");
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_ = sim.AssertSqlError("""
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merge into v_pos using (values(1, -5)) src(id, v) on v_pos.id = src.id
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when not matched then insert (id, v) values (src.id, src.v);
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""", 550);
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}
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[TestMethod]
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public void CheckOption_UpdateViolation_RaisesMsg550()
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{
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var sim = new Simulation();
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sim.ExecuteBatches(
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"create table base_t (id int primary key, v int); insert base_t values (1, 10)",
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"create view v_pos as select id, v from base_t where v > 0 with check option");
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_ = sim.AssertSqlError("""
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merge into v_pos using (values(1, -1)) src(id, v) on v_pos.id = src.id
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when matched then update set v = src.v;
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""", 550);
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}
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[TestMethod]
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public void NonUpdatableView_RaisesMsg4405()
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{
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// Multi-base view (join) — not updatable.
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var sim = new Simulation();
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sim.ExecuteBatches(
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"create table a (id int primary key, v int); create table b (id int primary key, v int)",
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"create view v_join as select a.id, a.v as av, b.v as bv from a join b on a.id = b.id");
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_ = sim.AssertSqlError("""
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merge into v_join using (values(1, 1, 1)) src(id, av, bv) on v_join.id = src.id
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when not matched then insert (id, av, bv) values (src.id, src.av, src.bv);
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""", 4405);
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}
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[TestMethod]
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public void InsteadOfInsertTrigger_FiresInsteadOfHeapWrite()
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{
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// INSTEAD OF INSERT routes through the trigger; the base table sees
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// no writes from the MERGE itself — only what the trigger body does.
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var sim = new Simulation();
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sim.ExecuteBatches(
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"create table base_t (id int primary key, v int)",
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"create table log_t (id int identity, msg varchar(50))",
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"create view v_base as select id, v from base_t",
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"create trigger tr_v_ins on v_base instead of insert as begin insert into log_t (msg) values ('fired'); insert into base_t select * from inserted; end",
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"""
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merge into v_base using (values(1, 10)) src(id, v) on v_base.id = src.id
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when not matched then insert (id, v) values (src.id, src.v);
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""");
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AreEqual(1, sim.ExecuteScalar("select count(*) from log_t"));
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AreEqual(1, sim.ExecuteScalar("select count(*) from base_t"));
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AreEqual(10, sim.ExecuteScalar("select v from base_t where id = 1"));
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}
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[TestMethod]
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public void InsteadOfUpdateTrigger_FiresInsteadOfHeapWrite()
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{
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// INSTEAD OF UPDATE: the heap row stays put unless the trigger
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// explicitly mutates it; the trigger gets INSERTED/DELETED in
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// view shape.
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var sim = new Simulation();
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sim.ExecuteBatches(
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"create table base_t (id int primary key, v int); insert base_t values (1, 0)",
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"create table log_t (id int identity, before_v int, after_v int)",
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"create view v_base as select id, v from base_t",
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"create trigger tr_v_upd on v_base instead of update as insert into log_t (before_v, after_v) select d.v, i.v from inserted i join deleted d on i.id = d.id",
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"""
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merge into v_base using (values(1, 99)) src(id, v) on v_base.id = src.id
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when matched then update set v = src.v;
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""");
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AreEqual(1, sim.ExecuteScalar("select count(*) from log_t"));
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AreEqual(0, sim.ExecuteScalar("select before_v from log_t"));
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AreEqual(99, sim.ExecuteScalar("select after_v from log_t"));
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AreEqual(0, sim.ExecuteScalar("select v from base_t where id = 1"));
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}
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[TestMethod]
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public void InsteadOfDeleteTrigger_FiresInsteadOfHeapWrite()
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{
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var sim = new Simulation();
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sim.ExecuteBatches(
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"create table base_t (id int primary key, v int); insert base_t values (1, 10)",
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"create table log_t (id int identity, msg varchar(50))",
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"create view v_base as select id, v from base_t",
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"create trigger tr_v_del on v_base instead of delete as insert into log_t (msg) values ('deleted')",
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"""
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merge into v_base using (values(1, 99)) src(id, v) on v_base.id = src.id
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when matched then delete;
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""");
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AreEqual(1, sim.ExecuteScalar("select count(*) from log_t"));
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AreEqual(1, sim.ExecuteScalar("select count(*) from base_t"));
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}
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[TestMethod]
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public void DerivedColumn_WriteRejected_Msg4406()
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{
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// View projects a computed column; writes to it raise Msg 4406.
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var sim = new Simulation();
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sim.ExecuteBatches(
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"create table base_t (id int primary key, v int)",
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"create view v_derived as select id, v, v * 2 as doubled from base_t");
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_ = sim.AssertSqlError("""
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merge into v_derived using (values(1, 10, 20)) src(id, v, doubled) on v_derived.id = src.id
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when not matched then insert (id, v, doubled) values (src.id, src.v, src.doubled);
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""", 4406);
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}
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[TestMethod]
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public void DerivedColumn_OmittedFromInsert_Works()
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{
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// Same view, but the INSERT only writes the non-derived columns.
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var sim = new Simulation();
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sim.ExecuteBatches(
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"create table base_t (id int primary key, v int)",
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"create view v_derived as select id, v, v * 2 as doubled from base_t",
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"""
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merge into v_derived using (values(1, 7)) src(id, v) on v_derived.id = src.id
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when not matched then insert (id, v) values (src.id, src.v);
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""");
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AreEqual(7, sim.ExecuteScalar("select v from base_t where id = 1"));
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AreEqual(14, sim.ExecuteScalar("select doubled from v_derived where id = 1"));
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}
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[TestMethod]
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public void OutputThroughView_RaisesNotSupported()
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{
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var sim = new Simulation();
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sim.ExecuteBatches(
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"create table base_t (id int primary key, v int)",
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"create view v_base as select id, v from base_t");
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_ = Throws<System.NotSupportedException>(() => sim.ExecuteNonQuery("""
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merge into v_base using (values(1, 10)) src(id, v) on v_base.id = src.id
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when not matched then insert (id, v) values (src.id, src.v) output inserted.id;
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"""));
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}
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[TestMethod]
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public void ViewWithAlias_Works()
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{
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var sim = new Simulation();
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sim.ExecuteBatches(
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"create table base_t (id int primary key, v int)",
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"create view v_base as select id, v from base_t",
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"""
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merge into v_base as v using (values(1, 10)) src(id, v) on v.id = src.id
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when not matched then insert (id, v) values (src.id, src.v);
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""");
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AreEqual(10, sim.ExecuteScalar("select v from base_t where id = 1"));
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}
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}

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