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嵌入式数据库sqlite 3.5.9的文档

<p>P2 is the number of arguments that the step function takes and
P4 is a pointer to the FuncDef for this function.  The P2
argument is not used by this opcode.  It is only there to disambiguate
functions that can take varying numbers of arguments.  The
P4 argument is only needed for the degenerate case where
the step function was not previously called.</td></tr>
<tr><td valign="top" align="center">
<a name="AggStep"></a><p>AggStep</p>
<td><p>Execute the step function for an aggregate.  The
function has P5 arguments.   P4 is a pointer to the FuncDef
structure that specifies the function.  Use register
P3 as the accumulator.</p>

<p>The P5 arguments are taken from register P2 and its
successors.</td></tr>
<tr><td valign="top" align="center">
<a name="And"></a><p>And</p>
<td><p>Take the logical AND of the values in registers P1 and P2 and
write the result into register P3.</p>

<p>If either P1 or P2 is 0 (false) then the result is 0 even if
the other input is NULL.  A NULL and true or two NULLs give
a NULL output.</td></tr>
<tr><td valign="top" align="center">
<a name="AutoCommit"></a><p>AutoCommit</p>
<td><p>Set the database auto-commit flag to P1 (1 or 0). If P2 is true, roll
back any currently active btree transactions. If there are any active
VMs (apart from this one), then the COMMIT or ROLLBACK statement fails.</p>

<p>This instruction causes the VM to halt.</td></tr>
<tr><td valign="top" align="center">
<a name="BitAnd"></a><p>BitAnd</p>
<td><p>Take the bit-wise AND of the values in register P1 and P2 and
store the result in register P3.
If either input is NULL, the result is NULL.</td></tr>
<tr><td valign="top" align="center">
<a name="BitNot"></a><p>BitNot</p>
<td><p>Interpret the content of register P1 as an integer.  Replace it
with its ones-complement.  If the value is originally NULL, leave
it unchanged.</td></tr>
<tr><td valign="top" align="center">
<a name="BitOr"></a><p>BitOr</p>
<td><p>Take the bit-wise OR of the values in register P1 and P2 and
store the result in register P3.
If either input is NULL, the result is NULL.</td></tr>
<tr><td valign="top" align="center">
<a name="Blob"></a><p>Blob</p>
<td><p>P4 points to a blob of data P1 bytes long.  Store this
blob in register P2. This instruction is not coded directly
by the compiler. Instead, the compiler layer specifies
an OP_HexBlob opcode, with the hex string representation of
the blob as P4. This opcode is transformed to an OP_Blob
the first time it is executed.</td></tr>
<tr><td valign="top" align="center">
<a name="Clear"></a><p>Clear</p>
<td><p>Delete all contents of the database table or index whose root page
in the database file is given by P1.  But, unlike Destroy, do not
remove the table or index from the database file.</p>

<p>The table being clear is in the main database file if P2==0.  If
P2==1 then the table to be clear is in the auxiliary database file
that is used to store tables create using CREATE TEMPORARY TABLE.</p>

<p>See also: Destroy</td></tr>
<tr><td valign="top" align="center">
<a name="Close"></a><p>Close</p>
<td><p>Close a cursor previously opened as P1.  If P1 is not
currently open, this instruction is a no-op.</td></tr>
<tr><td valign="top" align="center">
<a name="CollSeq"></a><p>CollSeq</p>
<td><p>P4 is a pointer to a CollSeq struct. If the next call to a user function
or aggregate calls sqlite3GetFuncCollSeq(), this collation sequence will
be returned. This is used by the built-in min(), max() and nullif()
functions.</p>

<p>The interface used by the implementation of the aforementioned functions
to retrieve the collation sequence set by this opcode is not available
publicly, only to user functions defined in func.c.</td></tr>
<tr><td valign="top" align="center">
<a name="Column"></a><p>Column</p>
<td><p>Interpret the data that cursor P1 points to as a structure built using
the MakeRecord instruction.  (See the MakeRecord opcode for additional
information about the format of the data.)  Extract the P2-th column
from this record.  If there are less that (P2+1)
values in the record, extract a NULL.</p>

<p>The value extracted is stored in register P3.</p>

<p>If the KeyAsData opcode has previously executed on this cursor, then the
field might be extracted from the key rather than the data.</p>

<p>If the column contains fewer than P2 fields, then extract a NULL.  Or,
if the P4 argument is a P4_MEM use the value of the P4 argument as
the result.</td></tr>
<tr><td valign="top" align="center">
<a name="Concat"></a><p>Concat</p>
<td><p>Add the text in register P1 onto the end of the text in
register P2 and store the result in register P3.
If either the P1 or P2 text are NULL then store NULL in P3.</p>

<p>P3 = P2 || P1</p>

<p>It is illegal for P1 and P3 to be the same register. Sometimes,
if P3 is the same register as P2, the implementation is able
to avoid a memcpy().</td></tr>
<tr><td valign="top" align="center">
<a name="ContextPop"></a><p>ContextPop</p>
<td><p>Restore the Vdbe context to the state it was in when contextPush was last
executed. The context stores the last insert row id, the last statement
change count, and the current statement change count.</td></tr>
<tr><td valign="top" align="center">
<a name="ContextPush"></a><p>ContextPush</p>
<td><p>Save the current Vdbe context such that it can be restored by a ContextPop
opcode. The context stores the last insert row id, the last statement change
count, and the current statement change count.</td></tr>
<tr><td valign="top" align="center">
<a name="Copy"></a><p>Copy</p>
<td><p>Make a copy of register P1 into register P2.</p>

<p>This instruction makes a deep copy of the value.  A duplicate
is made of any string or blob constant.  See also OP_SCopy.</td></tr>
<tr><td valign="top" align="center">
<a name="CreateIndex"></a><p>CreateIndex</p>
<td><p>Allocate a new index in the main database file if P1==0 or in the
auxiliary database file if P1==1 or in an attached database if
P1&gt;1.  Write the root page number of the new table into
register P2.</p>

<p>See documentation on OP_CreateTable for additional information.</td></tr>
<tr><td valign="top" align="center">
<a name="CreateTable"></a><p>CreateTable</p>
<td><p>Allocate a new table in the main database file if P1==0 or in the
auxiliary database file if P1==1 or in an attached database if
P1&gt;1.  Write the root page number of the new table into
register P2</p>

<p>The difference between a table and an index is this:  A table must
have a 4-byte integer key and can have arbitrary data.  An index
has an arbitrary key but no data.</p>

<p>See also: CreateIndex</td></tr>
<tr><td valign="top" align="center">
<a name="Delete"></a><p>Delete</p>
<td><p>Delete the record at which the P1 cursor is currently pointing.</p>

<p>The cursor will be left pointing at either the next or the previous
record in the table. If it is left pointing at the next record, then
the next Next instruction will be a no-op.  Hence it is OK to delete
a record from within an Next loop.</p>

<p>If the OPFLAG_NCHANGE flag of P2 is set, then the row change count is
incremented (otherwise not).</p>

<p>P1 must not be pseudo-table.  It has to be a real table with
multiple rows.</p>

<p>If P4 is not NULL, then it is the name of the table that P1 is
pointing to.  The update hook will be invoked, if it exists.
If P4 is not NULL then the P1 cursor must have been positioned
using OP_NotFound prior to invoking this opcode.</td></tr>
<tr><td valign="top" align="center">
<a name="Destroy"></a><p>Destroy</p>
<td><p>Delete an entire database table or index whose root page in the database
file is given by P1.</p>

<p>The table being destroyed is in the main database file if P3==0.  If
P3==1 then the table to be clear is in the auxiliary database file
that is used to store tables create using CREATE TEMPORARY TABLE.</p>

<p>If AUTOVACUUM is enabled then it is possible that another root page
might be moved into the newly deleted root page in order to keep all
root pages contiguous at the beginning of the database.  The former
value of the root page that moved - its value before the move occurred -
is stored in register P2.  If no page
movement was required (because the table being dropped was already
the last one in the database) then a zero is stored in register P2.
If AUTOVACUUM is disabled then a zero is stored in register P2.</p>

<p>See also: Clear</td></tr>
<tr><td valign="top" align="center">
<a name="Divide"></a><p>Divide</p>
<td><p>Divide the value in register P1 by the value in register P2
and store the result in register P3.  If the value in register P2
is zero, then the result is NULL.
If either input is NULL, the result is NULL.</td></tr>
<tr><td valign="top" align="center">
<a name="DropIndex"></a><p>DropIndex</p>
<td><p>Remove the internal (in-memory) data structures that describe
the index named P4 in database P1.  This is called after an index
is dropped in order to keep the internal representation of the
schema consistent with what is on disk.</td></tr>
<tr><td valign="top" align="center">
<a name="DropTable"></a><p>DropTable</p>
<td><p>Remove the internal (in-memory) data structures that describe
the table named P4 in database P1.  This is called after a table
is dropped in order to keep the internal representation of the
schema consistent with what is on disk.</td></tr>
<tr><td valign="top" align="center">
<a name="DropTrigger"></a><p>DropTrigger</p>
<td><p>Remove the internal (in-memory) data structures that describe
the trigger named P4 in database P1.  This is called after a trigger
is dropped in order to keep the internal representation of the
schema consistent with what is on disk.</td></tr>
<tr><td valign="top" align="center">
<a name="Eq"></a><p>Eq</p>
<td><p>This works just like the Lt opcode except that the jump is taken if
the operands in registers P1 and P3 are equal.
See the Lt opcode for additional information.</td></tr>
<tr><td valign="top" align="center">
<a name="Expire"></a><p>Expire</p>
<td><p>Cause precompiled statements to become expired. An expired statement
fails with an error code of SQLITE_SCHEMA if it is ever executed
(via sqlite3_step()).</p>

<p>If P1 is 0, then all SQL statements become expired. If P1 is non-zero,
then only the currently executing statement is affected.</td></tr>
<tr><td valign="top" align="center">
<a name="FifoRead"></a><p>FifoRead</p>
<td><p>Attempt to read a single integer from the Fifo.  Store that
integer in register P1.</p>

<p>If the Fifo is empty jump to P2.</td></tr>
<tr><td valign="top" align="center">
<a name="FifoWrite"></a><p>FifoWrite</p>
<td><p>Write the integer from register P1 into the Fifo.</td></tr>
<tr><td valign="top" align="center">
<a name="ForceInt"></a><p>ForceInt</p>
<td><p>Convert value in register P1 into an integer.  If the value
in P1 is not numeric (meaning that is is a NULL or a string that
does not look like an integer or floating point number) then
jump to P2.  If the value in P1 is numeric then
convert it into the least integer that is greater than or equal to its
current value if P3==0, or to the least integer that is strictly
greater than its current value if P3==1.</td></tr>
<tr><td valign="top" align="center">
<a name="Found"></a><p>Found</p>
<td><p>Register P3 holds a blob constructed by MakeRecord.  P1 is an index.
If an entry that matches the value in register p3 exists in P1 then
jump to P2.  If the P3 value does not match any entry in P1
then fall thru.  The P1 cursor is left pointing at the matching entry
if it exists.</p>

<p>This instruction is used to implement the IN operator where the
left-hand side is a SELECT statement.  P1 may be a true index, or it
may be a temporary index that holds the results of the SELECT
statement.   This instruction is also used to implement the
DISTINCT keyword in SELECT statements.</p>

<p>This instruction checks if index P1 contains a record for which
the first N serialised values exactly match the N serialised values
in the record in register P3, where N is the total number of values in
the P3 record (the P3 record is a prefix of the P1 record).</p>

<p>See also: NotFound, MoveTo, IsUnique, NotExists</td></tr>
<tr><td valign="top" align="center">
<a name="Function"></a><p>Function</p>
<td><p>Invoke a user function (P4 is a pointer to a Function structure that
defines the function) with P5 arguments taken from register P2 and
successors.  The result of the function is stored in register P3.