INSERT
INSERT — 在資料表中建立新的資料
語法
說明
INSERT inserts new rows into a table. One can insert one or more rows specified by value expressions, or zero or more rows resulting from a query.
The target column names can be listed in any order. If no list of column names is given at all, the default is all the columns of the table in their declared order; or the first N column names, if there are only N columns supplied by the VALUES clause or query. The values supplied by the VALUES clause or query are associated with the explicit or implicit column list left-to-right.
Each column not present in the explicit or implicit column list will be filled with a default value, either its declared default value or null if there is none.
If the expression for any column is not of the correct data type, automatic type conversion will be attempted.
The optional RETURNING clause causes INSERT to compute and return value(s) based on each row actually inserted (or updated, if an ON CONFLICT DO UPDATE clause was used). This is primarily useful for obtaining values that were supplied by defaults, such as a serial sequence number. However, any expression using the table's columns is allowed. The syntax of the RETURNING list is identical to that of the output list of SELECT. Only rows that were successfully inserted or updated will be returned. For example, if a row was locked but not updated because an ON CONFLICT DO UPDATE ... WHERE clause condition was not satisfied, the row will not be returned.
You must have INSERT privilege on a table in order to insert into it. If ON CONFLICT DO UPDATE is present, UPDATE privilege on the table is also required.
If a column list is specified, you only need INSERT privilege on the listed columns. Similarly, when ON CONFLICT DO UPDATE is specified, you only need UPDATE privilege on the column(s) that are listed to be updated. However, ON CONFLICT DO UPDATE also requires SELECT privilege on any column whose values are read in the ON CONFLICT DO UPDATE expressions or condition.
Use of the RETURNING clause requires SELECT privilege on all columns mentioned in RETURNING. If you use the query clause to insert rows from a query, you of course need to have SELECT privilege on any table or column used in the query.
Parameters
Inserting
This section covers parameters that may be used when only inserting new rows. Parameters exclusively used with the ON CONFLICT clause are described separately.
with_query
It is possible for the query (SELECT statement) to also contain a WITH clause. In such a case both sets of with_query can be referenced within the query, but the second one takes precedence since it is more closely nested.
table_name
The name (optionally schema-qualified) of an existing table.
alias
A substitute name for table_name. When an alias is provided, it completely hides the actual name of the table. This is particularly useful when ON CONFLICT DO UPDATE targets a table named excluded, since that will otherwise be taken as the name of the special table representing rows proposed for insertion.
column_name
The name of a column in the table named by table_name. The column name can be qualified with a subfield name or array subscript, if needed. (Inserting into only some fields of a composite column leaves the other fields null.) When referencing a column with ON CONFLICT DO UPDATE, do not include the table's name in the specification of a target column. For example, INSERT INTO table_name ... ON CONFLICT DO UPDATE SET table_name.col = 1 is invalid (this follows the general behavior for UPDATE).
OVERRIDING SYSTEM VALUE
Without this clause, it is an error to specify an explicit value (other than DEFAULT) for an identity column defined as GENERATED ALWAYS. This clause overrides that restriction.
OVERRIDING USER VALUE
If this clause is specified, then any values supplied for identity columns defined as GENERATED BY DEFAULT are ignored and the default sequence-generated values are applied.
This clause is useful for example when copying values between tables. Writing INSERT INTO tbl2 OVERRIDING USER VALUE SELECT * FROM tbl1 will copy from tbl1 all columns that are not identity columns in tbl2 while values for the identity columns in tbl2 will be generated by the sequences associated with tbl2.
DEFAULT VALUES
All columns will be filled with their default values. (An OVERRIDING clause is not permitted in this form.)
expression
An expression or value to assign to the corresponding column.
DEFAULT
The corresponding column will be filled with its default value.
query
output_expression
An expression to be computed and returned by the INSERT command after each row is inserted or updated. The expression can use any column names of the table named by table_name. Write * to return all columns of the inserted or updated row(s).
output_name
A name to use for a returned column.
ON CONFLICT Clause
ON CONFLICT Clause選用的 ON CONFLICT 子句指定了遭遇違反唯一性或提供排除約束違反錯誤的替代操作。對於建議插入的每個單獨資料，要就是繼續 INSERT，要就是如果違反了由 conflict_target 指定的約束條件或索引，則採用替代的 conflict_action。發生衝突時，CONFLICT DO NOTHING，只是避免插入一筆資料作為其替代操作。ON CONFLICT DO UPDATE 則以替代資料更新現有資料，如果建議插入的資料發生衝突的話。
conflict_target can perform unique index inference. When performing inference, it consists of one or more index_column_name columns and/or index_expression expressions, and an optional index_predicate. All table_name unique indexes that, without regard to order, contain exactly the conflict_target-specified columns/expressions are inferred (chosen) as arbiter indexes. If an index_predicate is specified, it must, as a further requirement for inference, satisfy arbiter indexes. Note that this means a non-partial unique index (a unique index without a predicate) will be inferred (and thus used by ON CONFLICT) if such an index satisfying every other criteria is available. If an attempt at inference is unsuccessful, an error is raised.
ON CONFLICT DO UPDATE guarantees an atomic INSERT or UPDATE outcome; provided there is no independent error, one of those two outcomes is guaranteed, even under high concurrency. This is also known as UPSERT — “UPDATE or INSERT”.
conflict_target
Specifies which conflicts ON CONFLICT takes the alternative action on by choosing arbiter indexes. Either performs unique index inference, or names a constraint explicitly. For ON CONFLICT DO NOTHING, it is optional to specify a conflict_target; when omitted, conflicts with all usable constraints (and unique indexes) are handled. For ON CONFLICT DO UPDATE, a conflict_target must be provided.
conflict_action
conflict_action specifies an alternative ON CONFLICT action. It can be either DO NOTHING, or a DO UPDATE clause specifying the exact details of the UPDATE action to be performed in case of a conflict. The SET and WHERE clauses in ON CONFLICT DO UPDATE have access to the existing row using the table's name (or an alias), and to rows proposed for insertion using the special excluded table. SELECT privilege is required on any column in the target table where corresponding excluded columns are read.
Note that the effects of all per-row BEFORE INSERT triggers are reflected in excluded values, since those effects may have contributed to the row being excluded from insertion.
index_column_name
The name of a table_name column. Used to infer arbiter indexes. Follows CREATE INDEX format. SELECT privilege on index_column_name is required.
index_expression
Similar to index_column_name, but used to infer expressions on table_name columns appearing within index definitions (not simple columns). Follows CREATE INDEX format. SELECT privilege on any column appearing within index_expression is required.
collation
When specified, mandates that corresponding index_column_name or index_expression use a particular collation in order to be matched during inference. Typically this is omitted, as collations usually do not affect whether or not a constraint violation occurs. Follows CREATE INDEX format.
opclass
When specified, mandates that corresponding index_column_name or index_expression use particular operator class in order to be matched during inference. Typically this is omitted, as the equality semantics are often equivalent across a type's operator classes anyway, or because it's sufficient to trust that the defined unique indexes have the pertinent definition of equality. Follows CREATE INDEX format.
index_predicate
Used to allow inference of partial unique indexes. Any indexes that satisfy the predicate (which need not actually be partial indexes) can be inferred. Follows CREATE INDEX format. SELECT privilege on any column appearing within index_predicate is required.
constraint_name
Explicitly specifies an arbiter constraint by name, rather than inferring a constraint or index.
condition
An expression that returns a value of type boolean. Only rows for which this expression returns true will be updated, although all rows will be locked when the ON CONFLICT DO UPDATE action is taken. Note that condition is evaluated last, after a conflict has been identified as a candidate to update.
Note that exclusion constraints are not supported as arbiters with ON CONFLICT DO UPDATE. In all cases, only NOT DEFERRABLE constraints and unique indexes are supported as arbiters.
INSERT with an ON CONFLICT DO UPDATE clause is a “deterministic” statement. This means that the command will not be allowed to affect any single existing row more than once; a cardinality violation error will be raised when this situation arises. Rows proposed for insertion should not duplicate each other in terms of attributes constrained by an arbiter index or constraint.
Note that it is currently not supported for the ON CONFLICT DO UPDATE clause of an INSERT applied to a partitioned table to update the partition key of a conflicting row such that it requires the row be moved to a new partition.
Tip
It is often preferable to use unique index inference rather than naming a constraint directly using ON CONFLICT ON CONSTRAINT constraint_name. Inference will continue to work correctly when the underlying index is replaced by another more or less equivalent index in an overlapping way, for example when using CREATE UNIQUE INDEX ... CONCURRENTLY before dropping the index being replaced.
Outputs
On successful completion, an INSERT command returns a command tag of the form
The count is the number of rows inserted or updated. oid is always 0 (it used to be the OID assigned to the inserted row if count was exactly one and the target table was declared WITH OIDS and 0 otherwise, but creating a table WITH OIDS is not supported anymore).
If the INSERT command contains a RETURNING clause, the result will be similar to that of a SELECT statement containing the columns and values defined in the RETURNING list, computed over the row(s) inserted or updated by the command.
Notes
If the specified table is a partitioned table, each row is routed to the appropriate partition and inserted into it. If the specified table is a partition, an error will occur if one of the input rows violates the partition constraint.
Examples
Insert a single row into table films:
In this example, the len column is omitted and therefore it will have the default value:
This example uses the DEFAULT clause for the date columns rather than specifying a value:
To insert a row consisting entirely of default values:
To insert multiple rows using the multirow VALUES syntax:
This example inserts some rows into table films from a table tmp_films with the same column layout as films:
This example inserts into array columns:
Insert a single row into table distributors, returning the sequence number generated by the DEFAULT clause:
Increment the sales count of the salesperson who manages the account for Acme Corporation, and record the whole updated row along with current time in a log table:
Insert or update new distributors as appropriate. Assumes a unique index has been defined that constrains values appearing in the did column. Note that the special excluded table is used to reference values originally proposed for insertion:
Insert a distributor, or do nothing for rows proposed for insertion when an existing, excluded row (a row with a matching constrained column or columns after before row insert triggers fire) exists. Example assumes a unique index has been defined that constrains values appearing in the did column:
Insert or update new distributors as appropriate. Example assumes a unique index has been defined that constrains values appearing in the did column. WHERE clause is used to limit the rows actually updated (any existing row not updated will still be locked, though):
Insert new distributor if possible; otherwise DO NOTHING. Example assumes a unique index has been defined that constrains values appearing in the did column on a subset of rows where the is_active Boolean column evaluates to true:
Compatibility
INSERT conforms to the SQL standard, except that the RETURNING clause is a PostgreSQL extension, as is the ability to use WITH with INSERT, and the ability to specify an alternative action with ON CONFLICT. Also, the case in which a column name list is omitted, but not all the columns are filled from the VALUES clause or query, is disallowed by the standard.
The SQL standard specifies that OVERRIDING SYSTEM VALUE can only be specified if an identity column that is generated always exists. PostgreSQL allows the clause in any case and ignores it if it is not applicable.
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